White undershirts

[Jimgolf]

I know the rules about undershirts, that they should match the predominant color of the players jerseys, but I'm wondering about the a-shirts or tank top undershirts that are not meant to be seen outside the jersey, but sometimes are visible. Do you have the players remove them, or do you let that slide? How about under-armor sleeveless undershirts?

It seems to me that officials in our area treat these undershirts similarly to when girls have sports bras that don't match the uniforms, but one official had a player remove his white a-shirt at a game this weekend. I don't recall any other official enforcing this, but maybe this is just the first time a player made an issue of it and I didn't notice before.