In the first picture the color comes from a sampled drumset where each part of the drum has a certain color, like kicks are red, toms are orange and snares are yellow.
In other cases you can see which keys are going to play a sound at all and you can see things like keyswitches (Those are used in certain sample libraries for violins and stuff like that where you have a few playstyles to choose from).
You can also set those lights to indicate certain scales, so you know which notes are part of the scale and which aren't.

But yeah, I'd say it's most useful for sample libraries where you have a variety of different sounds mapped across the keyboard at once.

Beside of those things, it just looks damn awesome