MD User Manager: Updates background color

chrome/browser/resources/md_user_manager/user_manager_tutorial.html

 <link rel="import" href="chrome://md-user-manager/shared_styles.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 
 <dom-module id="user-manager-tutorial">
   <template>
     <style include="shared-styles">
       .tutorial-slide {
         -webkit-transition: opacity 200ms ease-in-out;
@@ skipping 43 matching lines @@
         left: 20px;
         right: auto;
       }
 
       #notYou {
         height: 100px;
         width: 240px;
       }
 
       .slide-contents {
+        color: var(--primary-text-color);
         padding: 0 20px;
         text-align: center;
       }
 
       .slide-title {
-        color: black;
         font-size: 20px;
         line-height: 20px;
         margin: 30px 0;
       }
 
       .slide-text {
-        color: var(--google-grey-600);
         font-size: 15px;
         line-height: 20px;
       }
 
       .slide-buttons {
         bottom: 20px;
         position: absolute;
         text-align: center;
         width: 100%;
       }
@@ skipping 154 matching lines @@
               </a>
             </div>
           </div>
           <div class="arrow-down"></div>
         </div>
       </template>
     </template>
   </template>
   <script src="chrome://md-user-manager/user_manager_tutorial.js"></script>
 </dom-module>