Very fun and simple (in a good way) game. Reminds me of the old children's books where you had to spot the differences, or find Waldo. I love the hand drawn aesthetics. The replayability is also very good.
I would say that it could use a shakeup of the formula from level to level, perhaps make them move in different ways occasionally. I also think some of the colors are a little too similar. As someone that is not colorblind, I had trouble a little bit, which means it is probably unplayable for someone who is.
Nothing that can't be ironed out, though. Great job.