Comment by poopchute

I'm pretty sure this only affects protan(omaly/opia). The green and red cones along with the rods all play a roll in determining the brightness of any colour. When the red cone is shifted towards green, then all wavelengths to the right of that will be darkened. I thought tritanopia would experience this too since the blue cone is also an edge-of-the-rainbow cone, but apparently the blue cone plays a very small roll in detecting brightness. Therefore, a bright blue colour would appear to to someone with tritanopia as yellowish white, since it is nearly equally detected by the green & red cones.