Errr......Blue is on the opposite side of the spectrum from red, so I would actually be following a fine system.
I'd rather it go Blue -> Purple up and Orange -> Red down than Green -> Blue -> Purple up and Orange -> Red down. I don't need three full colors to do 5 different types of matchups, especially when 2 of those are very rare.
The only difference is that I'm skipping either Green or Yellow since they are both in the middle.I'll also eventually use green for 55:45, yellow-green for 50:50, and yellow for 45:55 I just didn't want to do it yet since for now one color is good enough for all three of those.
EDIT: additionally you must remember that Red and Green have stretches in the spectrum where they stay almost the same. If you remove these my color scheme accurately depicts the wavelength spectrum.
I'm pro at MS Paint, here
That has the long streaks of the same shade of red and green taken out, and I wrote what each color would be.