For ZE550ML/ZE551ML please update ASUS dialer & Contacts V1.7.0.22_150904
For other models, please download "ASUS Contacts Dark Theme-Dark" from Google Play store and update ASUS dialer & Contacts to V1.7.0.22_150904.
Please notice this function support on Andriod Lollipop(5.0) or later version.
Setup:
1. Access settings in Contacts page.
2. Tap [Personalized Settings].
3. Tick [Dark mode].
4. Now you can see the screen change to dark theme in ASUS dialer & Contacts 。