See graph above.

Increasing amounts of white or amber light entering the eye causes a proportional increase in migraine pain. But, both blue and red light, regardless of intensity, always causes sever migraine pain. Amazingly, very low amounts of only-pure green light entering the eye is very soothing. As the brightness of green light entering the eye increases, it becomes less soothing. Once the brightness of pure green light entering the eye becomes very bright, then it starts to become mildly migraine pain increasing.

This research paper is totally free in its entirety and can be found by clicking here.