I ordered a white shirt a while back it's definitely not a miracle shirt .. however it does help and works for some of my shirts that I wear for work.
I still felt sweaty but at least the sweat didn't show through my shirt. Well I ordered a black one and wore it today with a grey work shirt. I was embarrassed!! The second one I ordered did nothing I sweat through my shirt! :/
I'm not sure if the color of the shirt had anything to do with it or not.  But I'm sending it back $30 for an undershirt, I expect it to work!