Colour, i.e. indications with two or more different colours

Full Title

Input/output interfacing specifically adapted for electrophonic musical tools or instruments > Indicator, i.e. non-screen output user interfacing, e.g. visual or tactile instrument status or guidance information using lights, LEDs or seven segments displays > associated with a key or other user input device, e.g. key indicator lights > LED, i.e. using a light-emitting diode as indicator > Colour, i.e. indications with two or more different colours