Why would your wife have a problem? It's none of her concern. simply hand your wife the shirt and she should make it bright and new again, you don't need to explain yourself. Are you the man of the house? Tee Hee
Yeah right.. accidentally touched her lips to your shirt?! And it was your collar? what an interesting "accident". Your wife should throw your cheating ass out the door!
If you have a lipstick smudge on your white shirt or collar try sparying it with hairspary allow the hair spary to sit for a minute or two then wipe ot with a clean white cloth the lipstick should come off