Is it inappropriate to tell a random woman, "You look good in that color"?

I noticed a woman in the store who really put a lot of effort in how she looked on that day. She looked sad I ran into her a coupe times in the store. When I was leaving the store I noticed her again and I said to her "You know you really look stunning." Made her day.

Edited to add, she was around my age so it wasn't like I was creeping on her.