Fun little game! I'd say up through the first forty levels or so, it's easy but not effortless, very relaxing. Around the forties it starts to require more active thought and effort, and becomes more challenging. Both are appealing in their own way. As a game strongly reliant on color matching, this game isn't going to work well for you if you have limited color vision, but otherwise it's pretty accessible to all players and runs smoothly. If this sounds like your thing, give it a whirl!
I've played through the whole thing just now, it starts pretty simple but there are a few tougher puzzles towards the end
Excellent!
If you like to sort colors, this game might be even better:
https://play.google.com/store/apps/details?id=com.zutgames.ilovehue
Interesting concept, but it's crashing as soon as I get past the beginner levels