Very much plays like a metroidvania, you get stronger weapons and new abilities etc.. The art is pretty damn alright for being a solo dev and having a month's time. Are the guards a 3D render?
I feel like some weapons made me too overpowered (the spear and huge sword), and most enemies were a breeze to kill. I had insane range and damage. Do different colored enemies mean they have more health and/or strength?
I guess music variation would've been nice to accompany the colorswap levels, just to give it a little more variation despite your limited dev resources.
The final boss was.. disappointingly easy as he hardly attacked me. There was no real mechanic to the boss other than to whack like you've been doing and poof he ded. It's not a big complaint but I guess you had time constraints.
Finally, I feel like the levels had too many stretches of walks with not much interesting going on. I'd add more decoration and maybe more variation in the platforming (think about spikes, swinging maces, flying axes,..). If you purposefully made this decision I respect that though. I just feel like it missed something to make the levels themselves more interesting.
Good job on making the title card and some of the graphics and congratulations for making it to the end of the jam! I did play through the whole game so it didn't really bore me which is a good sign!