What is with boys and how they can only wear plain white tee’s for undershirts.  This I understand since you dont want any writing coming through to your other shirt.  Thats fine.

But the thing that I dont get, is why are these tee shirts good enough to be undershirts but you can’t wear them by themselves, unless your going to sleep in it.

Is there some rule that I never caught before on white tee shirts and when and how you can wear them? 

It’s just another shirt, your going to work in it and get it dirty.  I dont think that anyone really cares if you are wearing a plain white tee or a blue one or green one or whatever color.  It’s a shirt, and its clean so why not wear it.