Colour Music

Do all colours lighten and darken at the same rate? The physicists might know. I don’t, but I wonder. All I could do was demonstrate the thought. It is subjective, but it seemed to me that colours like yellow and red are brighter by nature than green and blue. So, at what point is a red and a blue equally bright? I decided that the obvious thing to do was to separate colours into these two groups accordingly, then divide them again into lighter and darker shades. To make a musical analogy, I ended up with four chords; light reds; dark reds; light blues and dark blues. Each, four shades, or notes on a scale.