If APDL is showing a different color theme than you like or are accustomed to, you can change this setting under Settings > General. The color theme is set by default to Auto mode which will follow the iOS color theme setting. If you have the iOS color them setting set to automatically change based on a time or sunrise/sunset, APDL will also change color theme at different times of day as iOS changes theme. You can lock the color theme in APDL by setting it to Dark or Light at all times.