A long time ago when reddit wasn't as noticably awful, I read a comment there pointing out that while women receive lots of questionably-motivated compliments from thirsty men, men themselves rarely receive compliments and even a passing one can change someone's day. I'm a man and can confirm at least the second half of that.
Since then, I've done my best to flatter anyone - whether presenting as man or woman - who does anything that stands out (I try not to comment on something that wasn't a conscious decision, like body parts). Loud shirt? Awesome! Unnaturally colored hair? I love it! Something that took effort, like a perm? You know I'm expressing my approval. Especially in a situation where I'm just passing by someone I'll never see again and therefore (hopefully) obviously not trying to get something from them.
I like to think I've improved some people's days with this policy. One of my favorite memories is of a situation where I demonstrably did so (I've actually referenced it on Lemmy before, a long time ago).
edit: Remove unneeded words.