Complimenting people can feel like a shameful act. But, I've tried to learn to not be ashamed about being genuinely complimentary as long as I'm not being a creep or intrusive about it.

• That's a great color on you!
• Random thing I admire about you that you clearly chose or cultivated.
• Somebody here is wearing an amazing perfume/cologne.
• You handled that situation with a grace/creativity/enthusiasm that I envy.
• Your's was a truly insightful or creative take.
• NOT comments on the things about themselves they have little or no control over (like height for men, or breast size for women. You're complimenting people not objects).

I like to just drop the genuinely positive truth bombs and walk away like a geriatric crop dusting the early bird special. They (the target of said compliment) should not feel obligated to acknowledge reciprocate in any way. This suddenly feels shamefully long winded. Be cool to each other.