The 15-50% is apprently women who have some sensitivity to different color bands, but not full terrachromacy. That condition has only been identified once according to wikipedia. Id expect in men with XXY chromosomes, for it to still be stunningly rare, if even present at all.

Its fully possible that the above sum is the number of men with some enhanced color depth, but even then in a population of 4 billion, 1-4 million is a very small number.