diff --git a/Lib/ufoLib/__init__.py b/Lib/ufoLib/__init__.py
index 7ebcb7a4e..768ab1f78 100755
--- a/Lib/ufoLib/__init__.py
+++ b/Lib/ufoLib/__init__.py
@@ -363,7 +363,7 @@ class UFOReader(object):
 		if not self._checkForFile(path):
 			return {}
 		data = self._readPlist(path)
-		valid, message = libValidator(data)
+		valid, message = fontLibValidator(data)
 		if not valid:
 			raise UFOLibError(message)
 		return data
@@ -828,7 +828,7 @@ class UFOWriter(object):
 		Write lib.plist. This method requires a
 		lib dict as an argument.
 		"""
-		valid, message = libValidator(libDict)
+		valid, message = fontLibValidator(libDict)
 		if not valid:
 			raise UFOLibError(message)
 		self._makeDirectory()
diff --git a/Lib/ufoLib/glifLib.py b/Lib/ufoLib/glifLib.py
index 51f340139..14659e88f 100755
--- a/Lib/ufoLib/glifLib.py
+++ b/Lib/ufoLib/glifLib.py
@@ -19,7 +19,7 @@ from robofab.pens.pointPen import AbstractPointPen
 from plistlib import readPlist, writePlistToString
 from filenames import userNameToFileName
 from validators import isDictEnough, genericTypeValidator, colorValidator,\
-	guidelinesValidator, anchorsValidator, identifierValidator, imageValidator, libValidator
+	guidelinesValidator, anchorsValidator, identifierValidator, imageValidator, glyphLibValidator
 
 try:
 	set
@@ -988,7 +988,7 @@ def _readLib(glyphObject, children):
 	from plistFromTree import readPlistFromTree
 	assert len(children) == 1
 	lib = readPlistFromTree(children[0])
-	valid, message = libValidator(lib)
+	valid, message = glyphLibValidator(lib)
 	if not valid:
 		raise GlifLibError(message)
 	_relaxedSetattr(glyphObject, "lib", lib)
diff --git a/Lib/ufoLib/validators.py b/Lib/ufoLib/validators.py
index 19b16fe7b..05d5e786d 100644
--- a/Lib/ufoLib/validators.py
+++ b/Lib/ufoLib/validators.py
@@ -891,29 +891,29 @@ def groupsValidator(value):
 # lib.plist/lib
 # -------------
 
-def libValidator(value):
+def fontLibValidator(value):
 	"""
 	Check the validity of the lib.
 	Version 3+ (though it's backwards compatible with UFO 1 and UFO 2).
 
 	>>> lib = {"foo" : "bar"}
-	>>> libValidator(lib)
+	>>> fontLibValidator(lib)
 	(True, None)
 
 	>>> lib = {"public.awesome" : "hello"}
-	>>> libValidator(lib)
+	>>> fontLibValidator(lib)
 	(True, None)
 
 	>>> lib = {"public.glyphOrder" : ["A", "C", "B"]}
-	>>> libValidator(lib)
+	>>> fontLibValidator(lib)
 	(True, None)
 
 	>>> lib = {"public.glyphOrder" : "hello"}
-	>>> libValidator(lib)
+	>>> fontLibValidator(lib)
 	(False, 'public.glyphOrder is not properly formatted.')
 
 	>>> lib = {"public.glyphOrder" : ["A", 1, "B"]}
-	>>> libValidator(lib)
+	>>> fontLibValidator(lib)
 	(False, 'public.glyphOrder is not properly formatted.')
 	"""
 	bogusFormatMessage = "The lib data is not in the correct format."
@@ -932,6 +932,44 @@ def libValidator(value):
 					return False, bogusGlyphOrderMessage
 	return True, None
 
+# --------
+# GLIF lib
+# --------
+
+def glyphLibValidator(value):
+	"""
+	Check the validity of the lib.
+	Version 3+ (though it's backwards compatible with UFO 1 and UFO 2).
+
+	>>> lib = {"foo" : "bar"}
+	>>> glyphLibValidator(lib)
+	(True, None)
+
+	>>> lib = {"public.awesome" : "hello"}
+	>>> glyphLibValidator(lib)
+	(True, None)
+
+	>>> lib = {"public.markColor" : "1,0,0,0.5"}
+	>>> glyphLibValidator(lib)
+	(True, None)
+
+	>>> lib = {"public.markColor" : 1}
+	>>> glyphLibValidator(lib)
+	(False, 'public.markColor is not properly formatted.')
+	"""
+	bogusFormatMessage = "The lib data is not in the correct format."
+	if not isDictEnough(value):
+		return False, bogusFormatMessage
+	for key, value in value.items():
+		if not isinstance(key, basestring):
+			return False, bogusFormatMessage
+		# public.markColor
+		if key == "public.markColor":
+			if not colorValidator(value):
+				return False, "public.markColor is not properly formatted."
+	return True, None
+
+
 if __name__ == "__main__":
 	import doctest
 	doctest.testmod()