Hah, I’m gonna use this as an insult from now on. You know the type of people that it will work on the best. You know, the ones calling everyone snowflakes, but for some reason they get offended at the slightest thing? Those.
The joke explained: Reservoir dogs the film on the man’s T-shirt has many characters who use aliases like 'Mr. Blue" or “Mr. Orange”. The joke is that all of them side by side creates a rainbow.