As a mid-50s dude I avoid complimenting young women if they look nice because it would seem kind of creepy.
I was in a store the other day and saw a woman (guessing in her late 60s) with long white hair and a pretty face that left me breathless.
I was very tempted to remark about how good she looked, but held off. If I was single I would have gone for it, but I wasn't trying to pick her up.
Should I have said something?
Something like, "I just wanted to say that you're extremely beautiful" is nice.