I was watching another Friends episode where Ross his looking for one of his missing shirts. He asks the other friends if they have seen his "salmon-colored shirt" and they say, "you mean the pink one?". Ross corrects them and says that it is salmon colored.
Ross doesn't want to admit that the shirt is pink because it will make him less macho if it is. Although the shirt is very close to the color pink, he refuses to call it that because guys usually do not wear wear pink shirts. If they do, they are considered less manly. He doesn't want to be joked by his friends for wearing pink so he labels the color himself and sets the record straight. By calling it a salmon colored shirt, it makes it less girl for him to wear it.
This raises the question again- Why does society say that men are not supposed to wear pink colored shirts? It is because the color pink is associated with the female sex and not the male sex.
Ross loves this shirt so much and when he realizes that he left it at his ex-girlfriend's apartment, he breaks in to get it back. When she catches him and asks if she can keep it to remember him by, he says no and snatches it away from her. This brings him back into male dominance by having authority and getting what he wants- which is the shirt.