diff --git a/src/builtin/color/other.rs b/src/builtin/color/other.rs
index cac8ae2..15e4e5e 100644
--- a/src/builtin/color/other.rs
+++ b/src/builtin/color/other.rs
@@ -3,8 +3,12 @@ use super::GlobalFunctionMap;
 use num_traits::{One, Signed, Zero};
 
 use super::Builtin;
+use crate::args::CallArgs;
 use crate::color::Color;
 use crate::common::QuoteKind;
+use crate::error::SassResult;
+use crate::scope::Scope;
+use crate::selector::Selector;
 use crate::unit::Unit;
 use crate::value::{Number, Value};
 
@@ -51,7 +55,11 @@ macro_rules! opt_hsl {
 }
 
 pub(crate) fn register(f: &mut GlobalFunctionMap) {
-    f.insert("change-color", Builtin::new(|mut args, scope, super_selector| {
+    fn change_color(
+        mut args: CallArgs,
+        scope: &Scope,
+        super_selector: &Selector,
+    ) -> SassResult<Value> {
         if args.get_positional(1, scope, super_selector).is_some() {
             return Err(
                 ("Only one positional argument is allowed. All other arguments must be passed by name.", args.span()
@@ -60,9 +68,13 @@ pub(crate) fn register(f: &mut GlobalFunctionMap) {
 
         let color = match arg!(args, scope, super_selector, 0, "color") {
             Value::Color(c) => c,
-            v => return Err(
-                (format!("$color: {} is not a color.", v.to_css_string(args.span())?), args.span()
-            ).into()),
+            v => {
+                return Err((
+                    format!("$color: {} is not a color.", v.to_css_string(args.span())?),
+                    args.span(),
+                )
+                    .into())
+            }
         };
 
         opt_rgba!(args, alpha, "alpha", 0, 1, scope, super_selector);
@@ -71,24 +83,46 @@ pub(crate) fn register(f: &mut GlobalFunctionMap) {
         opt_rgba!(args, blue, "blue", 0, 255, scope, super_selector);
 
         if red.is_some() || green.is_some() || blue.is_some() {
-            return Ok(Value::Color(Box::new(Color::from_rgba(red.unwrap_or(color.red()), green.unwrap_or(color.green()), blue.unwrap_or(color.blue()), alpha.unwrap_or(color.alpha())))))
+            return Ok(Value::Color(Box::new(Color::from_rgba(
+                red.unwrap_or(color.red()),
+                green.unwrap_or(color.green()),
+                blue.unwrap_or(color.blue()),
+                alpha.unwrap_or(color.alpha()),
+            ))));
         }
 
-        let hue = match named_arg!(args, scope, super_selector, "hue"=Value::Null) {
+        let hue = match named_arg!(args, scope, super_selector, "hue" = Value::Null) {
             Value::Dimension(n, _) => Some(n),
             Value::Null => None,
-            v => return Err(
-                (format!("$hue: {} is not a number.", v.to_css_string(args.span())?), args.span()
-            ).into()),
+            v => {
+                return Err((
+                    format!("$hue: {} is not a number.", v.to_css_string(args.span())?),
+                    args.span(),
+                )
+                    .into())
+            }
         };
 
-        opt_hsl!(args, saturation, "saturation", 0, 100, scope, super_selector);
+        opt_hsl!(
+            args,
+            saturation,
+            "saturation",
+            0,
+            100,
+            scope,
+            super_selector
+        );
         opt_hsl!(args, luminance, "lightness", 0, 100, scope, super_selector);
 
         if hue.is_some() || saturation.is_some() || luminance.is_some() {
             // Color::as_hsla() returns more exact values than Color::hue(), etc.
             let (this_hue, this_saturation, this_luminance, this_alpha) = color.as_hsla();
-            return Ok(Value::Color(Box::new(Color::from_hsla(hue.unwrap_or(this_hue), saturation.unwrap_or(this_saturation), luminance.unwrap_or(this_luminance), alpha.unwrap_or(this_alpha)))))
+            return Ok(Value::Color(Box::new(Color::from_hsla(
+                hue.unwrap_or(this_hue),
+                saturation.unwrap_or(this_saturation),
+                luminance.unwrap_or(this_luminance),
+                alpha.unwrap_or(this_alpha),
+            ))));
         }
 
         Ok(Value::Color(if let Some(a) = alpha {
@@ -96,197 +130,242 @@ pub(crate) fn register(f: &mut GlobalFunctionMap) {
         } else {
             color
         }))
-    }));
-    f.insert(
-        "adjust-color",
-        Builtin::new(|mut args, scope, super_selector| {
-            let color = match arg!(args, scope, super_selector, 0, "color") {
-                Value::Color(c) => c,
-                v => {
-                    return Err((
-                        format!("$color: {} is not a color.", v.to_css_string(args.span())?),
-                        args.span(),
-                    )
-                        .into())
-                }
-            };
-
-            opt_rgba!(args, alpha, "alpha", -1, 1, scope, super_selector);
-            opt_rgba!(args, red, "red", -255, 255, scope, super_selector);
-            opt_rgba!(args, green, "green", -255, 255, scope, super_selector);
-            opt_rgba!(args, blue, "blue", -255, 255, scope, super_selector);
-
-            if red.is_some() || green.is_some() || blue.is_some() {
-                return Ok(Value::Color(Box::new(Color::from_rgba(
-                    color.red() + red.unwrap_or(Number::zero()),
-                    color.green() + green.unwrap_or(Number::zero()),
-                    color.blue() + blue.unwrap_or(Number::zero()),
-                    color.alpha() + alpha.unwrap_or(Number::zero()),
-                ))));
-            }
-
-            let hue = match named_arg!(args, scope, super_selector, "hue" = Value::Null) {
-                Value::Dimension(n, _) => Some(n),
-                Value::Null => None,
-                v => {
-                    return Err((
-                        format!("$hue: {} is not a number.", v.to_css_string(args.span())?),
-                        args.span(),
-                    )
-                        .into())
-                }
-            };
-
-            opt_hsl!(
-                args,
-                saturation,
-                "saturation",
-                -100,
-                100,
-                scope,
-                super_selector
-            );
-            opt_hsl!(
-                args,
-                luminance,
-                "lightness",
-                -100,
-                100,
-                scope,
-                super_selector
-            );
-
-            if hue.is_some() || saturation.is_some() || luminance.is_some() {
-                // Color::as_hsla() returns more exact values than Color::hue(), etc.
-                let (this_hue, this_saturation, this_luminance, this_alpha) = color.as_hsla();
-                return Ok(Value::Color(Box::new(Color::from_hsla(
-                    this_hue + hue.unwrap_or(Number::zero()),
-                    this_saturation + saturation.unwrap_or(Number::zero()),
-                    this_luminance + luminance.unwrap_or(Number::zero()),
-                    this_alpha + alpha.unwrap_or(Number::zero()),
-                ))));
-            }
-
-            Ok(Value::Color(if let Some(a) = alpha {
-                let temp_alpha = color.alpha();
-                Box::new(color.with_alpha(temp_alpha + a))
-            } else {
-                color
-            }))
-        }),
-    );
-    f.insert(
-        "scale-color",
-        Builtin::new(|mut args, scope, super_selector| {
-            let span = args.span();
-            let color = match arg!(args, scope, super_selector, 0, "color") {
-                Value::Color(c) => c,
-                v => return Err(
-                    (format!("$color: {} is not a color.", v.to_css_string(span)?), span
-                ).into()),
-            };
-
-            macro_rules! opt_scale_arg {
-                ($args:ident, $name:ident, $arg:literal, $low:literal, $high:literal, $scope:ident, $super_selector:ident) => {
-                    let $name = match named_arg!($args, $scope, $super_selector, $arg = Value::Null) {
-                        Value::Dimension(n, Unit::Percent) => {
-                            Some(bound!($args, $arg, n, Unit::Percent, $low, $high) / Number::from(100))
-                        }
-                        v @ Value::Dimension(..) => {
-                            return Err(
-                                (format!("${}: Expected {} to have unit \"%\".", $arg, v.to_css_string($args.span())?), $args.span()).into()
-                            )
-                        }
-                        Value::Null => None,
-                        v => return Err(
-                            (format!("${}: {} is not a number.", $arg, v.to_css_string($args.span())?), $args.span()
-                        ).into()),
-                    };
-                };
-            }
-
-            opt_scale_arg!(args, alpha, "alpha", -100, 100, scope, super_selector);
-            opt_scale_arg!(args, red, "red", -100, 100, scope, super_selector);
-            opt_scale_arg!(args, green, "green", -100, 100, scope, super_selector);
-            opt_scale_arg!(args, blue, "blue", -100, 100, scope, super_selector);
-
-            if red.is_some() || green.is_some() || blue.is_some() {
-                return Ok(Value::Color(Box::new(Color::from_rgba(
-                    scale(
-                        color.red(),
-                        red.unwrap_or(Number::zero()),
-                        Number::from(255),
-                    ),
-                    scale(
-                        color.green(),
-                        green.unwrap_or(Number::zero()),
-                        Number::from(255),
-                    ),
-                    scale(
-                        color.blue(),
-                        blue.unwrap_or(Number::zero()),
-                        Number::from(255),
-                    ),
-                    scale(
-                        color.alpha(),
-                        alpha.unwrap_or(Number::zero()),
-                        Number::one(),
-                    ),
-                ))));
-            }
-
-            opt_scale_arg!(args, saturation, "saturation", -100, 100, scope, super_selector);
-            opt_scale_arg!(args, luminance, "lightness", -100, 100, scope, super_selector);
-
-            if saturation.is_some() || luminance.is_some() {
-                // Color::as_hsla() returns more exact values than Color::hue(), etc.
-                let (this_hue, this_saturation, this_luminance, this_alpha) = color.as_hsla();
-                return Ok(Value::Color(Box::new(Color::from_hsla(
-                    scale(this_hue, Number::zero(), Number::from(360)),
-                    scale(
-                        this_saturation,
-                        saturation.unwrap_or(Number::zero()),
-                        Number::one(),
-                    ),
-                    scale(
-                        this_luminance,
-                        luminance.unwrap_or(Number::zero()),
-                        Number::one(),
-                    ),
-                    scale(this_alpha, alpha.unwrap_or(Number::zero()), Number::one()),
-                ))));
-            }
-
-            Ok(Value::Color(if let Some(a) = alpha {
-                let temp_alpha = color.alpha();
-                Box::new(color.with_alpha(scale(temp_alpha, a, Number::one())))
-            } else {
-                color
-            }))
-        }),
-    );
-    f.insert(
-        "ie-hex-str",
-        Builtin::new(|mut args, scope, super_selector| {
-            args.max_args(1)?;
-            let color = match arg!(args, scope, super_selector, 0, "color") {
-                Value::Color(c) => c,
-                v => {
-                    return Err((
-                        format!("$color: {} is not a color.", v.to_css_string(args.span())?),
-                        args.span(),
-                    )
-                        .into())
-                }
-            };
-            Ok(Value::Ident(color.to_ie_hex_str(), QuoteKind::None))
-        }),
-    );
-}
-
-fn scale(val: Number, by: Number, max: Number) -> Number {
-    if by.is_zero() {
-        return val;
     }
-    val.clone() + (if by.is_positive() { max - val } else { val }) * by
+
+    fn adjust_color(
+        mut args: CallArgs,
+        scope: &Scope,
+        super_selector: &Selector,
+    ) -> SassResult<Value> {
+        let color = match arg!(args, scope, super_selector, 0, "color") {
+            Value::Color(c) => c,
+            v => {
+                return Err((
+                    format!("$color: {} is not a color.", v.to_css_string(args.span())?),
+                    args.span(),
+                )
+                    .into())
+            }
+        };
+
+        opt_rgba!(args, alpha, "alpha", -1, 1, scope, super_selector);
+        opt_rgba!(args, red, "red", -255, 255, scope, super_selector);
+        opt_rgba!(args, green, "green", -255, 255, scope, super_selector);
+        opt_rgba!(args, blue, "blue", -255, 255, scope, super_selector);
+
+        if red.is_some() || green.is_some() || blue.is_some() {
+            return Ok(Value::Color(Box::new(Color::from_rgba(
+                color.red() + red.unwrap_or(Number::zero()),
+                color.green() + green.unwrap_or(Number::zero()),
+                color.blue() + blue.unwrap_or(Number::zero()),
+                color.alpha() + alpha.unwrap_or(Number::zero()),
+            ))));
+        }
+
+        let hue = match named_arg!(args, scope, super_selector, "hue" = Value::Null) {
+            Value::Dimension(n, _) => Some(n),
+            Value::Null => None,
+            v => {
+                return Err((
+                    format!("$hue: {} is not a number.", v.to_css_string(args.span())?),
+                    args.span(),
+                )
+                    .into())
+            }
+        };
+
+        opt_hsl!(
+            args,
+            saturation,
+            "saturation",
+            -100,
+            100,
+            scope,
+            super_selector
+        );
+        opt_hsl!(
+            args,
+            luminance,
+            "lightness",
+            -100,
+            100,
+            scope,
+            super_selector
+        );
+
+        if hue.is_some() || saturation.is_some() || luminance.is_some() {
+            // Color::as_hsla() returns more exact values than Color::hue(), etc.
+            let (this_hue, this_saturation, this_luminance, this_alpha) = color.as_hsla();
+            return Ok(Value::Color(Box::new(Color::from_hsla(
+                this_hue + hue.unwrap_or(Number::zero()),
+                this_saturation + saturation.unwrap_or(Number::zero()),
+                this_luminance + luminance.unwrap_or(Number::zero()),
+                this_alpha + alpha.unwrap_or(Number::zero()),
+            ))));
+        }
+
+        Ok(Value::Color(if let Some(a) = alpha {
+            let temp_alpha = color.alpha();
+            Box::new(color.with_alpha(temp_alpha + a))
+        } else {
+            color
+        }))
+    }
+
+    fn scale_color(
+        mut args: CallArgs,
+        scope: &Scope,
+        super_selector: &Selector,
+    ) -> SassResult<Value> {
+        fn scale(val: Number, by: Number, max: Number) -> Number {
+            if by.is_zero() {
+                return val;
+            }
+            val.clone() + (if by.is_positive() { max - val } else { val }) * by
+        }
+
+        let span = args.span();
+        let color = match arg!(args, scope, super_selector, 0, "color") {
+            Value::Color(c) => c,
+            v => {
+                return Err((
+                    format!("$color: {} is not a color.", v.to_css_string(span)?),
+                    span,
+                )
+                    .into())
+            }
+        };
+
+        macro_rules! opt_scale_arg {
+            ($args:ident, $name:ident, $arg:literal, $low:literal, $high:literal, $scope:ident, $super_selector:ident) => {
+                let $name = match named_arg!($args, $scope, $super_selector, $arg = Value::Null) {
+                    Value::Dimension(n, Unit::Percent) => {
+                        Some(bound!($args, $arg, n, Unit::Percent, $low, $high) / Number::from(100))
+                    }
+                    v @ Value::Dimension(..) => {
+                        return Err((
+                            format!(
+                                "${}: Expected {} to have unit \"%\".",
+                                $arg,
+                                v.to_css_string($args.span())?
+                            ),
+                            $args.span(),
+                        )
+                            .into())
+                    }
+                    Value::Null => None,
+                    v => {
+                        return Err((
+                            format!(
+                                "${}: {} is not a number.",
+                                $arg,
+                                v.to_css_string($args.span())?
+                            ),
+                            $args.span(),
+                        )
+                            .into())
+                    }
+                };
+            };
+        }
+
+        opt_scale_arg!(args, alpha, "alpha", -100, 100, scope, super_selector);
+        opt_scale_arg!(args, red, "red", -100, 100, scope, super_selector);
+        opt_scale_arg!(args, green, "green", -100, 100, scope, super_selector);
+        opt_scale_arg!(args, blue, "blue", -100, 100, scope, super_selector);
+
+        if red.is_some() || green.is_some() || blue.is_some() {
+            return Ok(Value::Color(Box::new(Color::from_rgba(
+                scale(
+                    color.red(),
+                    red.unwrap_or(Number::zero()),
+                    Number::from(255),
+                ),
+                scale(
+                    color.green(),
+                    green.unwrap_or(Number::zero()),
+                    Number::from(255),
+                ),
+                scale(
+                    color.blue(),
+                    blue.unwrap_or(Number::zero()),
+                    Number::from(255),
+                ),
+                scale(
+                    color.alpha(),
+                    alpha.unwrap_or(Number::zero()),
+                    Number::one(),
+                ),
+            ))));
+        }
+
+        opt_scale_arg!(
+            args,
+            saturation,
+            "saturation",
+            -100,
+            100,
+            scope,
+            super_selector
+        );
+        opt_scale_arg!(
+            args,
+            luminance,
+            "lightness",
+            -100,
+            100,
+            scope,
+            super_selector
+        );
+
+        if saturation.is_some() || luminance.is_some() {
+            // Color::as_hsla() returns more exact values than Color::hue(), etc.
+            let (this_hue, this_saturation, this_luminance, this_alpha) = color.as_hsla();
+            return Ok(Value::Color(Box::new(Color::from_hsla(
+                scale(this_hue, Number::zero(), Number::from(360)),
+                scale(
+                    this_saturation,
+                    saturation.unwrap_or(Number::zero()),
+                    Number::one(),
+                ),
+                scale(
+                    this_luminance,
+                    luminance.unwrap_or(Number::zero()),
+                    Number::one(),
+                ),
+                scale(this_alpha, alpha.unwrap_or(Number::zero()), Number::one()),
+            ))));
+        }
+
+        Ok(Value::Color(if let Some(a) = alpha {
+            let temp_alpha = color.alpha();
+            Box::new(color.with_alpha(scale(temp_alpha, a, Number::one())))
+        } else {
+            color
+        }))
+    }
+
+    fn ie_hex_str(
+        mut args: CallArgs,
+        scope: &Scope,
+        super_selector: &Selector,
+    ) -> SassResult<Value> {
+        args.max_args(1)?;
+        let color = match arg!(args, scope, super_selector, 0, "color") {
+            Value::Color(c) => c,
+            v => {
+                return Err((
+                    format!("$color: {} is not a color.", v.to_css_string(args.span())?),
+                    args.span(),
+                )
+                    .into())
+            }
+        };
+        Ok(Value::Ident(color.to_ie_hex_str(), QuoteKind::None))
+    }
+
+    f.insert("change-color", Builtin::new(change_color));
+    f.insert("adjust-color", Builtin::new(adjust_color));
+    f.insert("scale-color", Builtin::new(scale_color));
+    f.insert("ie-hex-str", Builtin::new(ie_hex_str));
 }