[dump121]

That's too broad / vague. I understand that if my actions/words are making/will make other person uncomfortable, I should stop. But if a coworker changed her hair style and I complemented it, can I be legally complained against?

[susanrigetti]

The parent comment is not correct. No, you will not be "legally complained against" (I think you mean "am I breaking the law") if you compliment your coworker's hairstyle. See this: https://www.eeoc.gov/laws/types/sexual_harassment.cfm