I hadn't noticed Leo's arm, due to the color matching you mentioned.
It also works well with these two mobsters. It really does blend right in, unless you know to look for it.
Don't worry, I won't sing like a canary about your secret. I don't want to wear cement overshoes.
Btw, if they were holding what Troi was holding, they would undoubtedly be ready for a piece of the action. ;-)