By giving only 3 choices, and none of the choices being the equivalent of "I don't know, I see no number, only dots" one is forced to guess. By guessing, even a (color)blind squirrel can find a nut.
I am known, diagnosed by a university medical center, as Red-Green color blind. I saw some of the figures in the start, then they became increasingly difficult to see anything but dots. So, I guessed. It said I got 6 wrong. Well there were lots more than that, where I had ZERO clue, as to what I was looking at. If you're going to make it a test, make it one that will be graded fairly.
Junk, complete junk.