Changes color scheme of alt keys.

ui/keyboard/resources/elements/kb-key.html

 <!--
   -- Copyright 2013 The Chromium Authors. All rights reserved.
   -- Use of this source code is governed by a BSD-style license that can be
   -- found in the LICENSE file.
   -->
 
 <polymer-element name="kb-key" extends="kb-key-base" attributes="image keyCode
     keyName shiftModifier sound stretch weight">
   <template>
     <style>
@@ skipping 41 matching lines @@
       :host([image]) .key {
         height: 30%;
       }
 
       :host([image].tab) .key {
         height: 40%;
       }
 
       :host .hint,
       :host([invert]) key {
-        color: #bbbbbb;
+        color: #bababa;
       }
 
       :host .hint {
         font-size: 70%;
         position: absolute;
         right: 7%;
         top: 5%;
       }
 
       :host([invert]) .hint {
@@ skipping 30 matching lines @@
 </polymer-element>
 
 <!-- Special keys -->
 <polymer-element name="kb-abc-key" class="symbol dark" char="Invalid"
     extends="kb-key" weight="125">
 </polymer-element>
 
 <polymer-element name="kb-hide-keyboard-key" class="hide-keyboard dark"
     align="center" attributes="showMenu" char="Invalid" extends="kb-key">
 </polymer-element>