“Praising” someone without making them feel like they weren’t pretty before

Recently, Ive praised someone on their new hair dye, but I accidentally made them feel like their old hair color wasn't "worthy of praising". I don't want that to happen at all, ive been trying to be more social and polite, but I struggle with praising people without making them feeling like they need to compare themselves or get offended. (To clarify, this isn't about "suggestive" advice that would make me post this on another subreddit; I rarely see the person ive praised and only talk to them when I have to.)