Issue 7200 - Adjust UI colors

mobile/android/app/src/main/res/layout/tabs_panel_default.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- This Source Code Form is subject to the terms of the Mozilla Public
    - License, v. 2.0. If a copy of the MPL was not distributed with this
    - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
 
 <merge xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:gecko="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        tools:parentTag="LinearLayout"
        tools:layout_width="match_parent"
        tools:layout_height="match_parent"
        tools:background="@color/text_and_tabs_tray_grey"
        tools:orientation="vertical">
 
     <!-- The layout_height value is used in TabsPanel.getTabsLayoutContainerHeight
          and as an offset in PrivateTabsPanel: if you change it here,
          change it there! -->
     <RelativeLayout android:id="@+id/tabs_panel_header"
                     android:layout_width="match_parent"
                     android:layout_height="@dimen/browser_toolbar_height">
 
-        <!-- Using ABB color palette. See https://issues.adblockplus.org/ticket/3769 -->
         <view class="org.mozilla.gecko.tabs.TabsPanel$TabsPanelToolbar"
               android:layout_width="match_parent"
               android:layout_height="@dimen/browser_toolbar_height"
-              android:background="@color/abb_background_light_grey">
+              android:background="@color/text_and_tabs_tray_grey">
 
             <org.mozilla.gecko.tabs.TabPanelBackButton
                 android:id="@+id/nav_back"
                 android:layout_width="@dimen/tabs_panel_button_width"
                 android:layout_height="match_parent"
                 android:minWidth="@dimen/tabs_panel_button_width"
                 android:src="@drawable/tabs_panel_nav_back"
                 android:contentDescription="@string/back"
                 android:background="@drawable/action_bar_button_inverse"/>
 
@@ skipping 46 matching lines @@
 
         <org.mozilla.gecko.tabs.PrivateTabsPanel
                 android:id="@+id/private_tabs_panel"
                 android:layout_width="match_parent"
                 android:layout_height="match_parent"
                 android:visibility="gone"/>
 
     </FrameLayout>
 
 </merge>