Conclusion

Tuning System and Color Model


Based on the last induction, here, it got the notes and colors in the same wheel.  

Similar to the tuning systems in music, except 12-TET, there are others, like Just Intonation and Pythagorean. In color, there are also different models for color mixing, except RGB, CMYK, there is HSB (Hue, Saturation, Brightness). Considering octaves are repetitive, the whole pitch is lower or higher; from the listening experience, it sounds darker or brighter. Thus, HSB is a very suitable color model for the tuning system.   

We set the standard color in the wheel as C4. From C4 to C0, it goes to darker (B→0, S=100); from C4 to C8, it goes to brighter(B=100, S→0).



Application on 88 Keys



Based on the above, here is an 88-key piano.