Personally there's this girl I am hopelessly in love with and if she makes the slightest change to do with her appearance then my brain will clock it within two seconds of glimpsing her. When it comes to girls I am uninterested in I can still notice these things, however it takes slightly longer, but that's just because I'm over analytical about everything.
from my experience, when my ex started liking me and was interested, he would notice the shirts I wear and jewelry and would compliment me and stuff, so I do this is has to do with a guy being interested in you to notice, because that's how they analyze what you're all about your style and personality, they check you out head to toe even if you don't notice them checking you out trust me they do lol, theyre visual creatures after all
yeah they notice when you are looking especially nice, they might even compliment you and let you know
I don't think guys notice makeup unless you showed up one day with 10 lbs on when you normally wear none