Why? You can just use FILT + HEAT or FILT + COOL to color it, not that hard. Red FILT + Blue FILT = Violet photons.
We can doesn't mean we should.
I totally agree that the current way to color PHOT right is too troublesome and maybe difficult if you don't know binary numbers well. Sometimes you don't really need a precise wavelength because you just want to color it with a specific color but now the game mechanics is forcing you to compute the wavelength value to get that rgb value.
As you wish.