Engadget has publicized an unconfirmed rumor from NewTechSpy that Apple is working on incorporating color LCD buttons alongside the trackpad of future MacBooks. The new LCD keys would reportedly change their image based on what function they are assigned to.
The idea appears to be similar to the much publicized OLED Optimus keyboard which utilizes OLED screens for the physical keys, allowing images to be displayed on the keys themselves.
NewTechSpy has no previous history as a rumor source, so this should be taken cautiously.