The mantis shrimp has only 3 types of photoreceptors, like humans.
Why it is true
The mantis shrimp has between 12 and 16 types of photoreceptors, far more than the 3 in humans. Despite this, studies show it does not distinguish colours better than we do, which puzzles scientists.
Source: Journal of Experimental Biology
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.