My college roommate found out when I showed him a joke tshirt with a message in the circle of dots. He thought the joke was that there was nothing there and I w

My college roommate found out when I showed him a joke tshirt with a message in the circle of dots. He thought the joke was that there was nothing there and I was messing with him, then spent an hour on Wikipedia figuring out exactly what kind of color blindness he had.