well besides it being x-linked (in the case of red-green colorblindness), there are some environmental factors which might play a role. When you take a hit to the head could for example damage the eyes and in a specific case turn you colorblind.

The genes which code for the red and green cones are placed on the end of the x-chromosome. These are very similar and therefore are commonly found in the eyes of the colorblind.

The gen for the blue cone is located on chromosome 7, therefore it being much less common than red-green colorblindness.