That was a puzzle all right. I liked the simple visuals and the controls were snappy. Also enjoyed the slightly vague button tutorials, wanna do something like that for one of my games now >:)
Having a save system was much appreciated. It sadly didn't help much in the later levels (where I needed it the most) since it didn't save the single-press buttons' states and broke buttons if saved with a box on them. Also would put the save and load buttons further from each other, it's very easy to mispress K instead of L and lose all your progress. The buttons (at least the reset button) didn't work when I switched to a different language keyboard layout.
Explicitly telling the player that they softlocked themselves was pretty odd? More then once it acted as a straight up hint, and when it didn't, I knew that I softlocked myself without the text anyway. Also the softlock notification didn't disappear upon loading a save.
The levels were extremely hard to parse visually, which is somewhat integral to the mechanic I guess. You could preview the next aberration state with like 30% opacity at all times, not sure it would look good and/or understandable though, just an idea. Buttons could have been different for when they need a box and a single press, that's probably the biggest easily fixable problem. Could have been some portal-style background lines to show which button activates what.
The person below provided very good criticisms which I agree with completely so I'll try to not repeat what they said too much. The mechanic you came up with is pretty elegant and provides plenty of depth, I liked it; I didn't like the levels very much. The way I enjoy puzzles the most is when they have a tiny space with a small amount of possible permutations, focused on a single cool mechanical idea that makes me go "aha!" when I figure it out. This game had me go "oh, finally" when I solved a level. Instead of letting me experience a cool consequence of a mechanic, the game added five layers of complexity on top of it, making me completely overwhelmed, especially with already being fundamentally hard to parse due to the core mechanic. If I was making it, I would try to make every level as small as possible while keeping the singular thing that I find fun about the level. There's a good GDC talk that describes that for a bit.
The last mechanic with invisible colors is smart and could be nice in theory but it didn't work out well for me in the game; I didn't understand it at all in the introductory level and the last level wasn't satisfying to solve, felt somewhat like a chore to figure out. Also it obviously adds to the problem of levels being hard to visually parse.
This review is very critical but I did play for one and a half hours and beat it so clearly the game did something right! It is clever and made me proud of solving it. I also liked the dog in the end. Great job and good luck with your future games!