This app was removed from the App Store.
iOS Universal Entertainment
The color of this app is set based on how you tilt your device. Rotate your device like a steering wheel and you'll go through the whole spectrum of hues/colors. If your device has a compass, you can set the color based on your direction.
And of course, you can just double tap the screen for a white color (amazing, eh?).
iPhone 6 Optimized