Fix: crashes when applying css

color/color-common.ts

@@ -3,6 +3,7 @@ import types = require("utils/types");
 import knownColors = require("color/known-colors");
 
 var AMP = "#";
+var HEX_REGEX = /(^#[0-9A-F]{6}$)|(^#[0-9A-F]{3}$)/i;
 
 export class Color implements definition.Color {
     private _a: number;
@@ -107,6 +108,18 @@ export class Color implements definition.Color {
         return value1.equals(value2);
     }
 
+    public static isValid(value: string): boolean {
+        if (!types.isString(value)) {
+            return false;
+        }
+
+        if (knownColors.isKnownName(value)) {
+            return true;
+        }
+
+        return HEX_REGEX.test(value);
+    }
+
     private _buildHex(): string {
         return AMP + this._componentToHex(this._a) + this._componentToHex(this._r) + this._componentToHex(this._g) + this._componentToHex(this._b);
     }