If you use the stock Android keyboard, which is also available in the Play Store, you can change the look and feel of the keyboard. Google Keyboard has a few themes you can choose, but they’re not available in the settings.
Here’s a quick way to pick a different theme, assuming your device runs Android 4.0 or later:
1. you first need an application that lets you create shortcuts to app activities. Some apps that let you do that: Nova Launcher and Apex Launcher, probably the best Android launchers. The following instructions assume you’ve installed Nova Launcher or Apex Launcher, but you can also use simple apps like Activity Getter.
2. long press the homescreen and pick “shortcuts” and then “activities”.