Improve sleep by enabling red light:

iOS

1. Settings → Accessibility → Display & Text Size → Color Filters

2. Turn ON Color Filters → Select Color Tint

3. Set Intensity and Hue all the way to RED

4. Settings → Accessibility → Accessibility Shortcut → select Color Filters to toggle with triple-click on side button

Android

1. Settings → Display → Night Light or Eye Comfort Shield (name varies by device)

2. Turn ON and set schedule to Sunset to Sunrise

3. If available, adjust Color Temperature toward WARMEST setting

4. For deeper red, some phones support developer mode screen filters or third-party apps like Twilight or Red Moon