What halachot are affected if a person is colorblind? One probable example I can think of relates to the laws of niddah and checking emissions. Another less likely example would be the the halachic time defined by when a person can distinguish between leek-green and turquoise (though I doubt that this is really affected if a person is colorblind).
Note: There are various different types of color blindness, as described on Wikipedia. I am interested in how all of these affect halacha.
I can't think of any mitzva per se from which a colorblind individual would be exempted.
However there are judgement calls that an expert (usually a rabbi) has to make, some of which involve color. As you'd said, one of them is the color of certain stains with regards to nida. I know of a color-blind rabbi who does all sorts of leadership roles for his congregation, but has to send all "stain" questions to a congregant who has training in this area. A similar, though far less-weighty one, would be the occasional question of "is my etrog kosher?"
The earliest time for tefilin and tallit is when there's enough light in the sky for the average person to discern colors, it doesn't vary by person. (Otherwise a blind man would never be obligated in tallit, when in fact he is.)
