diff --git a/src/builtin/color.rs b/src/builtin/color.rs
index d41e7d6..c3ac2f3 100644
--- a/src/builtin/color.rs
+++ b/src/builtin/color.rs
@@ -1,23 +1,20 @@
 use std::collections::BTreeMap;
+use std::convert::TryInto;
 
 use super::Builtin;
 use crate::color::Color;
 use crate::value::Value;
 
 pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
-    f.insert(
-        "rgb".to_owned(),
-        Box::new(|args| {
-            let channels = args.get("channels").unwrap_or(&Value::Null);
-            if channels.is_null() {
-                let _red: &Value = arg!(args, 0, "red");
-                let _green: &Value = arg!(args, 1, "green");
-                let _blue: &Value = arg!(args, 2, "blue");
-            // Value::Color(Color::RGB(red, blue, green))
-            } else {
-                todo!("channels variable in `rgb`")
-            };
-            todo!()
-        }),
-    );
+    decl!(f "rgb", |args| {
+        let channels = args.get("channels").unwrap_or(&Value::Null);
+        if channels.is_null() {
+            let red: u16 = arg!(args, 0, "red").clone().try_into().unwrap();
+            let green: u16 = arg!(args, 1, "green").clone().try_into().unwrap();
+            let blue: u16 = arg!(args, 2, "blue").clone().try_into().unwrap();
+            Some(Value::Color(Color::from_values(red, green, blue, 1)))
+        } else {
+            todo!("channels variable in `rgb`")
+        }
+    });
 }
diff --git a/src/color/mod.rs b/src/color/mod.rs
index 3d10571..7107844 100644
--- a/src/color/mod.rs
+++ b/src/color/mod.rs
@@ -26,9 +26,9 @@ impl Color {
 
     pub fn from_values(red: u16, green: u16, blue: u16, alpha: u16) -> Self {
         let repr = if alpha >= 1 {
-            format!("#{:X}{:X}{:X}", red, green, blue)
+            format!("#{:0>2x}{:0>2x}{:0>2x}", red, green, blue)
         } else {
-            format!("#{:X}{:X}{:X}{:X}", red, green, blue, alpha)
+            format!("#{:0>2x}{:0>2x}{:0>2x}{:0>2x}", red, green, blue, alpha)
         };
         Color {
             red,
diff --git a/src/value.rs b/src/value.rs
index cdea1a5..61f269b 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -1,8 +1,12 @@
 #![allow(dead_code, unused_variables)]
+use std::convert::TryInto;
 use std::fmt::{self, Display};
 use std::iter::{Iterator, Peekable};
 use std::ops::{Add, Sub};
 
+use num_rational::BigRational;
+use num_bigint::BigInt;
+
 use crate::args::eat_call_args;
 use crate::builtin::GLOBAL_FUNCTIONS;
 use crate::color::Color;
@@ -70,7 +74,7 @@ pub(crate) enum Value {
     True,
     False,
     Null,
-    Dimension(Dimension, Unit),
+    Dimension(BigRational, Unit),
     List(Vec<Value>, ListSeparator),
     Color(Color),
     BinaryOp(Box<Value>, Op, Box<Value>),
@@ -214,6 +218,28 @@ impl Display for Value {
     }
 }
 
+impl TryInto<u16> for Value {
+    type Error = &'static str;
+    fn try_into(self) -> Result<u16, Self::Error> {
+        match self {
+            Self::Dimension(n, Unit::Percent) => {
+                todo!()
+            }
+            Self::Dimension(n, Unit::None) => {
+                if n >= BigRational::from_integer(BigInt::from(255)) {
+                    Ok(255)
+                } else {
+                    Ok(n.to_integer().to_str_radix(10).parse().unwrap())
+                }
+            }
+            Self::Dimension(n, _) => {
+                Err("Expected `val` to have no units or \"%\".")
+            }
+            _ => Err("expected number")
+        }
+    }
+}
+
 impl Value {
     pub fn is_null(&self) -> bool {
         self == &Value::Null
@@ -343,9 +369,7 @@ impl Value {
                     Unit::None
                 };
                 Some(Value::Dimension(
-                    Dimension {
-                        val: val.parse().unwrap(),
-                    },
+                    val.parse().expect("error parsing integer"),
                     unit,
                 ))
             }
diff --git a/tests/color.rs b/tests/color.rs
index 5faae05..7de5282 100644
--- a/tests/color.rs
+++ b/tests/color.rs
@@ -27,7 +27,17 @@ test!(preserves_hex_3_val_000, "a {\n  color: #000;\n}\n");
 test!(preserves_hex_3_val_123, "a {\n  color: #123;\n}\n");
 test!(preserves_hex_3_val_ab2, "a {\n  color: #ab2;\n}\n");
 // test!(
-//     ,
-//     "a {\n  color: OrAnGe;\n}\n",
-//     "a {\n  color: OrAnGe;\n}\n"
+//     converts_rgb_to_named_color,
+//     "a {\n  color: rgb(0, 0, 0);\n}\n",
+//     "a {\n  color: black;\n}\n"
 // );
+test!(
+    rgb_pads_0,
+    "a {\n  color: rgb(1, 2, 3);\n}\n",
+    "a {\n  color: #010203;\n}\n"
+);
+test!(
+    rgb_double_digits,
+    "a {\n  color: rgb(255, 255, 255);\n}\n",
+    "a {\n  color: #ffffff;\n}\n"
+);