Everyone’s got his own unique set of aesthetic sensibilities and ideal vision of beauty. In general, though, guys like looking at half-naked women, and when they aren’t in a position to look at one, they’ll settle for imagining them.
As such, it’s perfectly natural and healthy to fantasize about women wearing sexy lingerie if you’re a young man who’s reached the age of puberty (or if you’re an older man whose mind didn’t really progress that far afterwards). But when you start coming up with systems to determine what kind of lingerie a woman has on, like theorizing that it matches her umbrella, well, you might be thinking about women in their undies just a bit too much.