diff --git a/index.js b/index.js
index f6c9289..e74fcc3 100644
--- a/index.js
+++ b/index.js
@@ -36,7 +36,22 @@ function func(declarations, functions, functionMatcher, parseArgs) {
 
   declarations.forEach(function(decl){
     if ('comment' == decl.type) return;
-    var generatedFuncs = [], result, generatedFunc;
+    var replacedFunctions = [], replacedValues = [], result, replacedFunc, replacedValue;
+
+    var colorFunctionRegexPart = "(?:rgb|hsl)a?";
+    var colorMatcher = functionMatcherBuilder(colorFunctionRegexPart);
+    var replaceColorValues = function(value_str){
+      while (value_str.match(colorMatcher)) {
+        value_str = value_str.replace(colorMatcher, function(color, name, args){
+          replacedValue = {from: color, to: getRandomIdentifier(name)};
+          replacedValues.push(replacedValue);
+          return replacedValue.to;
+        });
+      }
+      return value_str;
+    };
+
+    decl.value = replaceColorValues(decl.value);
 
     while (decl.value.match(functionMatcher)) {
       decl.value = decl.value.replace(functionMatcher, function(_, name, args){
@@ -45,9 +60,17 @@ function func(declarations, functions, functionMatcher, parseArgs) {
         } else {
           args = [strip(args)];
         }
+        args = args.map(function(arg){
+          replacedValues.forEach(function(func) {
+            arg = arg.replace(func.to, func.from);
+          });
+          return arg;
+        });
         // Ensure result is string
         result = '' + functions[name].apply(decl, args);
 
+        result = replaceColorValues(result);
+
         // Prevent fall into infinite loop like this:
         //
         // {
@@ -56,16 +79,21 @@ function func(declarations, functions, functionMatcher, parseArgs) {
         //   }
         // }
         //
-        generatedFunc = {from: name, to: name + getRandomString()};
-        result = result.replace(functionMatcherBuilder(name), generatedFunc.to + '($2)');
-        generatedFuncs.push(generatedFunc);
+        replacedFunc = {from: name, to: getRandomIdentifier(name)};
+        result = result.replace(functionMatcherBuilder(name), replacedFunc.to + '($2)');
+        replacedFunctions.push(replacedFunc);
         return result;
       });
     }
 
-    generatedFuncs.forEach(function(func) {
+    replacedFunctions.forEach(function(func) {
+      decl.value = decl.value.replace(func.to, func.from);
+    });
+
+    replacedValues.forEach(function(func) {
       decl.value = decl.value.replace(func.to, func.from);
-    })
+    });
+
   });
 }
 
@@ -82,13 +110,13 @@ function functionMatcherBuilder(name) {
 }
 
 /**
- * get random string
+ * Generate a random string to use as an identifier replacing a function
  *
  * @api private
  */
 
-function getRandomString() {
-  return Math.random().toString(36).slice(2);
+function getRandomIdentifier(name) {
+  return name + Math.random().toString(36).slice(2);
 }
 
 /**
diff --git a/test/fixtures/function.colors.css b/test/fixtures/function.colors.css
new file mode 100644
index 0000000..de9bea6
--- /dev/null
+++ b/test/fixtures/function.colors.css
@@ -0,0 +1,4 @@
+.colorful {
+  border-color: ugly-border(rgba(203,10,200,0.3),#1D1F21,  hsl(320,50%,50%),hsla(230,90%,50%,0.7));
+}
+
diff --git a/test/fixtures/function.colors.nested.css b/test/fixtures/function.colors.nested.css
new file mode 100644
index 0000000..2a9939e
--- /dev/null
+++ b/test/fixtures/function.colors.nested.css
@@ -0,0 +1,4 @@
+.nested-color-calculation {
+  background-color: alpha(mix(#333, #FFF, 0.4), 0.8);
+}
+
diff --git a/test/fixtures/function.colors.nested.out.css b/test/fixtures/function.colors.nested.out.css
new file mode 100644
index 0000000..7d29a25
--- /dev/null
+++ b/test/fixtures/function.colors.nested.out.css
@@ -0,0 +1,4 @@
+.nested-color-calculation {
+  background-color: rgba(132, 132, 132, 0.8);
+}
+
diff --git a/test/fixtures/function.colors.out.css b/test/fixtures/function.colors.out.css
new file mode 100644
index 0000000..a25f3f3
--- /dev/null
+++ b/test/fixtures/function.colors.out.css
@@ -0,0 +1,4 @@
+.colorful {
+  border-color: rgba(203,10,200,0.3) #1D1F21 hsl(320,50%,50%) hsla(230,90%,50%,0.7);
+}
+
diff --git a/test/rework-function.js b/test/rework-function.js
index a7c1648..90f8c18 100644
--- a/test/rework-function.js
+++ b/test/rework-function.js
@@ -6,7 +6,10 @@ var rework = require('rework')
   , read = fs.readFileSync;
 
 function fixture(name) {
-  return read('test/fixtures/' + name + '.css', 'utf8').trim();
+  return read('test/fixtures/' + name + '.css', 'utf8')
+    .trim()
+    .replace(/\r\n/g, "\n")
+    .replace(/\t/g, "  ");
 }
 
 describe('.function()', function(){
@@ -50,4 +53,40 @@ describe('.function()', function(){
       return 'url(' + '/some/prefix' + path + ')';
     }
   })
+  
+  it('should support (function-like) color values as parameters', function() {
+    
+    rework(fixture('function.colors'))
+      .use(func({"ugly-border": uglyBorder}))
+      .toString()
+      .should.equal(fixture('function.colors.out'));
+
+    function uglyBorder(top, right, bottom, left){
+      return top + ' ' + right + ' ' + bottom + ' ' + left;
+    }
+  })
+  
+  it('should support (function-like) color values nested in parameters', function() {
+    
+    rework(fixture('function.colors.nested'))
+      .use(func({mix: mix, alpha: alpha}))
+      .toString()
+      .should.equal(fixture('function.colors.nested.out'));
+
+    function mix(colorA, colorB, x){
+      if(colorA === '#333' && colorB === '#FFF' && x == 0.4){
+        return 'rgb(132, 132, 132)';
+      }else{
+        throw new Error('Unexpected arguments to mix(): ' + [colorA, colorB, x]);
+      }
+    }
+
+    function alpha(color, x){
+      if(color === 'rgb(132, 132, 132)' && x == 0.8){
+        return 'rgba(132, 132, 132, 0.8)';
+      }else{
+        throw new Error('Unexpected arguments to alpha(): ' + [color, x]);
+      }
+    }
+  })
 })