Update dark theme color to match mock

Mock: https://docs.google.com/presentation/d/15JadcGi5k1_0znUN_XdFpU7UxeXwxjK3Y7LxvhW5ETM/edit?ts=5e1cc430#slide=id.g85fff7c452_76_21
Screenshot:
https://screenshot.googleplex.com/ytBaVdCCto0.png
https://screenshot.googleplex.com/TppopvRTG2t.png
https://screenshot.googleplex.com/cndtG9eKopv.png
https://screenshot.googleplex.com/0zPK9qaTqrY.png
https://screenshot.googleplex.com/mMRCbvq8AYT.png

Test: Manually
Fixes: 158587080
Change-Id: I48a20b13e133467d6e30c9c94ae0594df48cd019
diff --git a/res/layout/fragment_grid_picker.xml b/res/layout/fragment_grid_picker.xml
index 7f35689..84c8163 100644
--- a/res/layout/fragment_grid_picker.xml
+++ b/res/layout/fragment_grid_picker.xml
@@ -38,7 +38,7 @@
                 android:layout_height="0dp"
                 android:paddingTop="@dimen/preview_content_padding_top"
                 android:paddingBottom="@dimen/preview_content_padding_bottom"
-                android:background="@color/fullscreen_preview_background"
+                android:background="@color/preview_pager_background"
                 android:clipToPadding="false"
                 app:layout_constrainedHeight="true"
                 app:layout_constraintStart_toStartOf="parent"
diff --git a/res/layout/fragment_theme_picker.xml b/res/layout/fragment_theme_picker.xml
index a773207..2e3a6bb 100644
--- a/res/layout/fragment_theme_picker.xml
+++ b/res/layout/fragment_theme_picker.xml
@@ -36,7 +36,7 @@
                 android:layout_height="0dp"
                 android:paddingTop="@dimen/preview_content_padding_top"
                 android:paddingBottom="@dimen/preview_content_padding_bottom"
-                android:background="@color/fullscreen_preview_background"
+                android:background="@color/preview_pager_background"
                 android:clipToPadding="false"
                 app:layout_constrainedHeight="true"
                 app:layout_constraintStart_toStartOf="parent"
diff --git a/res/layout/theme_preview_color_icons.xml b/res/layout/theme_preview_color_icons.xml
index ccfb300..f1e7522 100644
--- a/res/layout/theme_preview_color_icons.xml
+++ b/res/layout/theme_preview_color_icons.xml
@@ -19,8 +19,7 @@
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:id="@+id/color_icons_section"
     android:layout_width="match_parent"
-    android:layout_height="match_parent"
-    android:background="@color/primary_color">
+    android:layout_height="match_parent">
 
     <androidx.constraintlayout.widget.ConstraintLayout
         android:layout_width="match_parent"
@@ -28,7 +27,8 @@
         android:paddingHorizontal="@dimen/preview_theme_color_icons_padding_horizontal"
         android:paddingTop="@dimen/preview_theme_color_icons_padding_top"
         android:paddingBottom="@dimen/preview_theme_color_icons_padding_bottom"
-        android:orientation="vertical">
+        android:orientation="vertical"
+        android:background="@color/theme_preview_color_icons_background">
 
         <!-- Title -->
         <TextView
@@ -37,6 +37,7 @@
             android:layout_height="wrap_content"
             android:text="@string/theme_preview_icons_section_title"
             android:textSize="@dimen/preview_theme_color_icons_title_text_size"
+            android:textColor="@color/theme_preview_color_icons_title_color"
             android:lineHeight="16dp"
             android:gravity="center"
             app:layout_constraintStart_toStartOf="parent"