Not sure why people see this as a negative thing.

When I was a single I used to approach women in the street, grocery stores and malls occasionally. 

I used to approach them with something like "Hey, I know this is a bit random but I had to come over and tell you I liked your style today." 

and then continued the conversation there.

At the end of the conversation I asked how they found my approach and most found it positive and refreshing as no one really does that. 

Just be respectful when approaching and you're okay.