Coloring of pitch classes according to the distance to the root of a key (in short key coloring) could be applied on real-world instruments, such as a piano keyboard or guitar fingerboard.
Each key on the keyboard (not to be confused with a diatonic key) could be colored according to the current diatonic key. This could hint the player which keys are likely to sound consonantly and which not.
It can be implemented in several ways:
- as an augmented-reality app - eg. on Google Glass
- by lighting the keys from inside (eg. by diodes)
- by projecting a pattern on the keyboard from a data projector
- by displaying a virtual colored keyboard just on a screen