why would you wear a white t shirt opposed to a blak one in winter
I would never wear a black shirt, unless I were playing Nathan Detroit in Guys and Dolls, or an SS officer in a war movie. I would not be good in either part.
A black shirt will radiate heat away faster, but the radiating is done in the infrared, where the emissivity may be unrelated to what it is in the visible part of the spectrum.