Type the name of a color to make it so. Perfect for three-year-olds:
http://stewd.io/colors
Yup. Just type a color name. (Or at least, one of the supported color names. I went for curation and simplicity here rather than infinite messiness. Say what you will.) The letters all appear as capitals since that’s what the little ones learn first—and that matches most keyboard keys. As soon as a color name is typed the background color will change appropriately. So fullscreen it, pull up your three-year-old, and give RED a shot since it’s a nice and short one with a vibrant pay off.
Simply added some languages that seemed like it would be nice to support. Perhaps having language packages that you can switch on and off would make even more sense, or simply recognize the language change... but these become less elegant and more than a code sketch.