I have vague recollections of having seen Color Zen on the Wii U and 3DS eShops, but it wasn't until the Switch port that I gave it a look. Apparently it was released for iOS first (not sure when the Android version came out). I'm not sure if the Switch port follows the format of that original release, but it provides 100+ puzzles for free, and then you can pay $1 for each of three additional downloadable puzzle packs. I'm guessing the Wii U and 3DS eShop versions just have you pay the $3 up front, though, and presumably have all the the DLC already included.
Anyway, at first I was impressed with the game's aesthetic and game mechanics, and they reminded me of Nintendo's Art Style series, which is high praise indeed as I consider them to be amongst the best puzzle games ever. The game's basic premise is that you have to move shapes around and combine ones that are the same color in order to merge them, which then fills the background with that color. There's a target color you have to end with, and some shapes are movable, and some are not. As you progress, the game introduces white shapes that can match any color, and black shapes that you can use to get rid of another shape. Like many modern puzzle games, the chill electronic soundtrack is absolutely essential in giving the game a cool and relaxing vibe, and the music perfectly complements the laid-back nature of the puzzle mechanics.
All well and good, and I really enjoyed the game starting off. However, the puzzles ended up being too shallow and repetitive, and by the time I got through the majority of the free levels I'd had enough. It looks like some of the DLC has more challenging puzzles, but as elegant as the core game mechanics are, they don't quite find the right balance between enjoyable and tedious as they increase in complexity. Tacking on more moves for each puzzle only makes them superficially more "difficult", and there were very few times where I had to stop and apply logic to make progress. By the end of the free puzzles I felt that the game mechanics had been thoroughly explored and exhausted, and even though 100+ levels isn't that much, it still felt like at least 1/3 of them were just basic repetition. Part of this feeling of repetition may be because of the game's mobile roots where you might just be doing a couple at a time while waiting for the bus or whatnot, but even then I don't think the game would've sustained my interest for very long past the initial set. I enjoyed giving the game a try, but it's too bad that it didn't have just a bit more in terms of interesting game mechanics.