diff --git a/toolkit/devtools/css-color.js b/toolkit/devtools/css-color.js
index 45340bd7447b..561240cfe6e3 100644
--- a/toolkit/devtools/css-color.js
+++ b/toolkit/devtools/css-color.js
@@ -57,7 +57,8 @@ function CssColor(colorValue) {
 module.exports.colorUtils = {
   CssColor: CssColor,
   rgbToHsl: rgbToHsl,
-  setAlpha: setAlpha
+  setAlpha: setAlpha,
+  classifyColor: classifyColor
 };
 
 /**
@@ -74,7 +75,10 @@ CssColor.COLORUNIT = {
 CssColor.prototype = {
   _colorUnit: null,
 
+  // The value as-authored.
   authored: null,
+  // A lower-cased copy of |authored|.
+  lowerCased: null,
 
   get colorUnit() {
     if (this._colorUnit === null) {
@@ -112,7 +116,7 @@ CssColor.prototype = {
   },
 
   get specialValue() {
-    return SPECIALVALUES.has(this.authored) ? this.authored : null;
+    return SPECIALVALUES.has(this.lowerCased) ? this.authored : null;
   },
 
   get name() {
@@ -171,8 +175,8 @@ CssColor.prototype = {
       return invalidOrSpecialValue;
     }
     if (!this.hasAlpha) {
-      if (this.authored.startsWith("rgb(")) {
-        // The color is valid and begins with rgb(. Return the authored value.
+      if (this.lowerCased.startsWith("rgb(")) {
+        // The color is valid and begins with rgb(.
         return this.authored;
       }
       let tuple = this._getRGBATuple();
@@ -186,8 +190,8 @@ CssColor.prototype = {
     if (invalidOrSpecialValue !== false) {
       return invalidOrSpecialValue;
     }
-    if (this.authored.startsWith("rgba(")) {
-      // The color is valid and begins with rgba(. Return the authored value.
+    if (this.lowerCased.startsWith("rgba(")) {
+      // The color is valid and begins with rgba(.
         return this.authored;
     }
     let components = this._getRGBATuple();
@@ -202,8 +206,8 @@ CssColor.prototype = {
     if (invalidOrSpecialValue !== false) {
       return invalidOrSpecialValue;
     }
-    if (this.authored.startsWith("hsl(")) {
-      // The color is valid and begins with hsl(. Return the authored value.
+    if (this.lowerCased.startsWith("hsl(")) {
+      // The color is valid and begins with hsl(.
       return this.authored;
     }
     if (this.hasAlpha) {
@@ -217,8 +221,8 @@ CssColor.prototype = {
     if (invalidOrSpecialValue !== false) {
       return invalidOrSpecialValue;
     }
-    if (this.authored.startsWith("hsla(")) {
-      // The color is valid and begins with hsla(. Return the authored value.
+    if (this.lowerCased.startsWith("hsla(")) {
+      // The color is valid and begins with hsla(.
       return this.authored;
     }
     if (this.hasAlpha) {
@@ -256,7 +260,11 @@ CssColor.prototype = {
    *         Any valid color string
    */
   newColor: function(color) {
-    this.authored = color.toLowerCase();
+    // Store a lower-cased version of the color to help with format
+    // testing.  The original text is kept as well so it can be
+    // returned when needed.
+    this.lowerCased = color.toLowerCase();
+    this.authored = color;
     return this;
   },
 
@@ -319,7 +327,7 @@ CssColor.prototype = {
   },
 
   _hsl: function(maybeAlpha) {
-    if (this.authored.startsWith("hsl(") && maybeAlpha === undefined) {
+    if (this.lowerCased.startsWith("hsl(") && maybeAlpha === undefined) {
       // We can use it as-is.
       return this.authored;
     }
@@ -415,6 +423,27 @@ function setAlpha(colorValue, alpha) {
   return "rgba(" + r + ", " + g + ", " + b + ", " + alpha + ")";
 }
 
+/**
+ * Given a color, classify its type as one of the possible color
+ * units, as known by |CssColor.colorUnit|.
+ *
+ * @param  {String} value
+ *         The color, in any form accepted by CSS.
+ * @return {String}
+ *         The color classification, one of "rgb", "hsl", "hex", or "name".
+ */
+function classifyColor(value) {
+  value = value.toLowerCase();
+  if (value.startsWith("rgb(") || value.startsWith("rgba(")) {
+    return CssColor.COLORUNIT.rgb;
+  } else if (value.startsWith("hsl(") || value.startsWith("hsla(")) {
+    return CssColor.COLORUNIT.hsl;
+  } else if (/^#[0-9a-f]+$/.exec(value)) {
+    return CssColor.COLORUNIT.hex;
+  }
+  return CssColor.COLORUNIT.name;
+}
+
 loader.lazyGetter(this, "DOMUtils", function () {
   return Cc["@mozilla.org/inspector/dom-utils;1"].getService(Ci.inIDOMUtils);
 });
diff --git a/toolkit/devtools/tests/unit/test_cssColor.js b/toolkit/devtools/tests/unit/test_cssColor.js
new file mode 100644
index 000000000000..b3e10a1c81ba
--- /dev/null
+++ b/toolkit/devtools/tests/unit/test_cssColor.js
@@ -0,0 +1,31 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test classifyColor.
+
+"use strict";
+
+const loader = new DevToolsLoader();
+const require = loader.require;
+const {colorUtils} = require("devtools/css-color");
+
+const CLASSIFY_TESTS = [
+  { input: "rgb(255,0,192)", output: "rgb" },
+  { input: "RGB(255,0,192)", output: "rgb" },
+  { input: "rgba(255,0,192, 0.25)", output: "rgb" },
+  { input: "hsl(5, 5, 5)", output: "hsl" },
+  { input: "hsla(5, 5, 5, 0.25)", output: "hsl" },
+  { input: "hSlA(5, 5, 5, 0.25)", output: "hsl" },
+  { input: "#f0c", output: "hex" },
+  { input: "#fe01cb", output: "hex" },
+  { input: "#FE01CB", output: "hex" },
+  { input: "blue", output: "name" },
+  { input: "orange", output: "name" }
+];
+
+function run_test() {
+  for (let test of CLASSIFY_TESTS) {
+    let result = colorUtils.classifyColor(test.input);
+    equal(result, test.output, "test classifyColor(" + test.input + ")");
+  }
+}
diff --git a/toolkit/devtools/tests/unit/xpcshell.ini b/toolkit/devtools/tests/unit/xpcshell.ini
index 94340145804d..9a1eafa729e8 100644
--- a/toolkit/devtools/tests/unit/xpcshell.ini
+++ b/toolkit/devtools/tests/unit/xpcshell.ini
@@ -16,6 +16,7 @@ support-files =
 [test_defineLazyPrototypeGetter.js]
 [test_async-utils.js]
 [test_consoleID.js]
+[test_cssColor.js]
 [test_prettifyCSS.js]
 [test_require_lazy.js]
 [test_require.js]