Darkroom Lab Timer - User Guide
You can change the screen color to provide red or green text by clicking the appropriate button at the top of the Timer screen. Green light is useful for developing film by inspection and red light allows handling of b&w paper and other materials in the darkroom. We recommend reducing brightness on your device as much as possible and keeping your device as far away from sensitive materials as practical. Always test for fogging prior to use as these Safelight modes are simulation-only and may not stop the device's white backlight from exposing sensitive material.
For additional protection you can also change the screen color to red at system level and use this in tandem with the the app's built-in red mode. In the Settings app select Accessibility > Color Filters. Turn the slider switch to the ON position and select Color Tint. Move both the Intensity and the Hue sliders to maximum position (right) and the screen will turn red. You can set up a shortcut to this feature by choosing Accessibility > Accessibility Shortcut in the Settings app, then enabling Color Filters. Using the shortcut, you can turn on the system-wide red filter by triple-clicking the Home button.
For additional protection you can use the Night Light feature to change the screen color to amber at system level and use this in tandem with the the app's built-in red mode. In the Settings app select Display > Night Light. Turn the Night Light ON, then move the Intensity slider to maximum position (right) and the screen will turn amber. There may be other ways to turn your screen red on a system-wide basis depending on your device manufacturer's extra Android features. We recommend you look in the Settings app for additional options (often found in the Accessibility menu). For instance, some Samsung phones will let you turn the screen red by using Accessibility > Vision > Color Lens.
One of the failings of the built-in safelight mode on newer versions of Android is the device's on-screen navigation buttons appear white. By using the method above, you can shift this color to amber (or red on some phones). If you are still concerned about white light leakage, you can further reduce this problem by removing the buttons altogether (Android 10+). To remove the Android navigation buttons, in the Settings app go to System > Gestures > System navigation and select Gesture navigation.