Add Color.toCssHexString and unit tests

CHANGES.md

@@ -4,6 +4,7 @@
 
 ##### Breaking Changes :mega:
 
+- Added `Color.toCssHexString` for getting the CSS hex string equivalent for a color.
 - Updated `WallGeometry` to respect the order of positions passed in, instead of making the positions respect a counter clockwise winding order. This will only effect the look of walls with an image material. If this changed the way your wall is drawing, reverse the order of the positions.
 
 ##### Additions :tada:

Source/Core/Color.js

@@ -632,6 +632,27 @@ Color.prototype.toCssColorString = function () {
   return "rgba(" + red + "," + green + "," + blue + "," + this.alpha + ")";
 };
 
+/**
+ * Creates a string containing CSS hex string color value for this color.
+ *
+ * @returns {String} The CSS hex string equivalent of this color.
+ */
+Color.prototype.toCssHexString = function () {
+  var r = Color.floatToByte(this.red).toString(16);
+  if (r.length < 2) {
+    r = "0" + r;
+  }
+  var g = Color.floatToByte(this.green).toString(16);
+  if (g.length < 2) {
+    g = "0" + g;
+  }
+  var b = Color.floatToByte(this.blue).toString(16);
+  if (b.length < 2) {
+    b = "0" + b;
+  }
+  return "#" + r + g + b;
+};
+
 /**
  * Converts this color to an array of red, green, blue, and alpha values
  * that are in the range of 0 to 255.

Specs/Core/ColorSpec.js

@@ -160,6 +160,15 @@ describe("Core/Color", function () {
     );
   });
 
+  it("toCssHexString produces expected output", function () {
+    expect(Color.WHITE.toCssHexString()).toEqual("#ffffff");
+    expect(Color.RED.toCssHexString()).toEqual("#ff0000");
+    expect(Color.BLUE.toCssHexString()).toEqual("#0000ff");
+    expect(Color.LIME.toCssHexString()).toEqual("#00ff00");
+    expect(new Color(0.0, 0.0, 0.0, 1.0).toCssHexString()).toEqual("#000000");
+    expect(new Color(0.1, 0.2, 0.3, 0.4).toCssHexString()).toEqual("#19334c");
+  });
+
   it("fromCssColorString supports transparent", function () {
     expect(Color.fromCssColorString("transparent")).toEqual(
       new Color(0.0, 0.0, 0.0, 0.0)