Android
Change Gboard Keyboard Theme auf Android
Android sets a neutral gray background on Gboard by default because the keyboard app, not the phone system, controls its own appearance. This is why you will not find a keyboard color option in the general Display settings - it lives inside Gboard's own preferences.
To change it, go to Tap on Settings ➔ Tap on System ➔ Tap on Keyboard ➔ Tap on On-screen keyboard ➔ Tap on Gboard ➔ Tap on Theme. From there you can pick a preset color, a gradient, or one of your own photos as the keyboard background.
After selecting a design, use the toggle to Turn on/off Key borders and confirm with Apply. Key borders draw a visible outline around each key, which helps if a busy photo background makes letters harder to read.
If your keyboard app is not Gboard but a third-party app, the theme option will not appear in this menu at all - each keyboard app manages its own appearance separately. In that case, open the third-party keyboard's own settings instead of the system Keyboard menu.
Changing the theme has no effect on autocorrect, typing speed, or layout - it only changes the visual background and key outlines.