Chrooma Keyboard
The private keyboard you were looking for it.
Screenshoot
My Comment
Love the app! RGB keyboard is the bomb and I don't think there's any other app which does it better than this one. The only complaint I have is that the app needs to keep on adding new words to the users dictionary so typing becomes smooth over time and the user does not have to go back to correct words which he typed correctly but it got corrected to some other word. Brilliant work on this app once again!
Definitely the best android keyboard out there. I love how the keyboard's colors just chances on each app.