I like the art of the game, and the option to change color palettes is fantastic. The music/SFX are also well-made. Everything about these elements feels very GameBoy-ish, which I think is great!
The foundation for good platformer gameplay is here as well, but unfortunately it is held back by a pretty major bug - the player character is "sticky" and won't move left or right at all unless in the air, meaning you have to spam the jump button to make any forward progress. The game is still completable because you can be next to a wall without being on the ground to initiate a jump, but the process of finishing the game basically boils down to spamming jump while holding D.
If this was an intentional gameplay design decision, I do apologize for mistaking it as a bug. This gameplay element wasn't advertised on the game page, so I just assumed it was a bug.
I hope this doesn't sound harsh, as I do respect the effort you have put into the game and think it's a nice project, but I hope the criticism is helpful as you continue to develop your game-making skills. We're right there with you - our game certainly ended up with a few problems too, lol
For a first-time GameJam project, this is good! I hope it has been a great learning experience for you and your team.