Add screen resource for Colors setting.

- each preference fragment should have its own preference screen layout
in order to show the title correctly. Adding the missing data for
ColorModePreferenceFragment.

Change-Id: I172429dc957f94351456d4bc829897a578d7dbf9
Fixes: 68763217
Test: make RunSettingsRoboTests

tests/robotests/src/com/android/settings/widget/RadioButtonPickerFragmentTest.java

@@ -113,6 +113,11 @@ public class RadioButtonPickerFragmentTest {
             return 0;
         }
 
+        @Override
+        protected int getPreferenceScreenResId() {
+            return 0;
+        }
+
         @Override
         protected List<DefaultAppInfo> getCandidates() {
             return new ArrayList<>();