How do you know if dogs are really color blind?

if you arent the eyes of a dog how would you know and are cats color blind
Scientists can tell by measuring the amount of cones in the eye. The cones are the structure that pick up on color. So the scientists have a way of measuring each type of cone and determining which of the types of cone it is, and being able to tell what color the eye can pick up. And by the way, dogs are not really colorblind any differently that humans are- they just don