I don’t understand this shirt. At first, I was completely confused, but after some searching, I realized that it was likely a reference to this shirt:
The second shirt is, in turn, a reference to Doppler shifting of light (which, among other things, says that colors shift towards blue if you move towards them quickly enough).
However, this just brings up more stuff I don’t understand:
(1) It doesn’t seem like the blue shirt makes any sense except as a reference to the red shirt. (Or does it?) But is the red shirt so well-known that it makes any sense to wear a shirt that assumes the viewer has seen the red one?
(2) The first shirt says “You don’t need run fast enough.” Is this slang? Or something English speakers might actually say? It doesn’t seem like it is, but I’m baffled by the idea that someone made and sold a T-shirt without proofreading the one sentence on the T-shirt. Yes, I see typos on signs and in newspaper articles all the time, this product only has one sentence, and that one sentence is the focus of the product that they’re trying to sell.
This seems very strange to me. Does this seem perfectly normal to you? Have you seen worse?