When I compare a red and green 507 Comp side by side, I can't detect any difference in the shape or quality of the 2 moa dot. Clearly different eyes perceive the dot differently.
What I can easily see, is that the green dot is effectively three clicks in intensity brighter than the red. In bright sun with sunglasses, the red 2 moa dot on the 507 Comp is too dim for me. Same with the 509T. The other reticles on the red 507 Comp are bright, just not the 2 moa dot.