What is the dispute betwen 6 or 7 colours of the spectrum (rainbow)?
There are an infinite number of colors in the visible spectrum. A computer display with 24 bit color only tells you that there are about 1400 colors of the rainbow (the others are attributes of saturation and brightness). People can distinguish red, orange, yellow, green, blue and violet. That is six colors. Previously, indigo had status in the spectrum, but people have trouble distinguishing it. I advocate for cyan to be added to the visible spectrum, because cyan is one of the primary colors of pigment, along with yellow and magenta, see your printer for details. Magenta is not part of the visible spectrum, and never will be, because magenta doesn’t exist as light on its own, but rather is your eye’s interpretation of red light mixed with blue light. Cyan light definitely exists, it is one of the spectrum lines of Hydrogen. I think people should be able to distinguish cyan from green and blue, better than they can distinguish indigo from blue and violet. The only reason I think that
