I really don't understand why you're getting down voted

People are probably down voting because op should own more than 1 work shirt. Shows some further issues beyond incorrect color but also hygiene as well..

My brother only has one work shirt I believe, and he works at Wendy's

My train of thought exactly :/ on top of it white the easiest one to get dirty.

Maybe his other shirts needed to be washed?

If op had more work shirts, op's brother probably would of just dyed them all lime green. =/

First thought. And besides just dirt, it gets to day 3 and starts to smell. No.

I have one work shirt. I just wash it a lot.

I've had two jobs where they only provided me with 1 or 2 shirts. I've found that uniform provided is often based on your contracted hours rather than how many hours you actually do. I was working 6-7 days a week, but because my contracted hours were only 8 hours a week I only got given part time uniform, which was based on me only working 2 days per week. It sucked big time.

my work only gave me one shirt despite multiple written requests. some employers aren't great at the kind of thing.

Or switch his shampoo with alcohol so when he puts it on his you run into the shower and throw a match or a lighter inside and set him on fire and laugh and say "look who is fired now!" ......maybe mine is going a little too far.

Or replace his shampoo with nair.

or.. it could be just far enough.

That is a bit too far 19, but it's creative and would definitely be poetic justice

... Nah, I think that's perfect!

Neon pink hair dye.

Well if you're working a minimum wage job, you are replaceable. That's how the roles are designed.

You would be surprised.

I wouldn't be allowed to work if my shirt was any other color than white. Probably not get fired for it, but I'd definitely get sent home.

That's what I was thinking at first too, fired over such a thing without even a warning first sounds highly questionable. Although if OP is employed as a casual he doesn't have many rights.