Although I have little to no authority on the matter, I’d like to share a quick pixel art tip I read from a guide somewhere. After drawing your art with black borders and filling in the proper color, a small way of improving the art is by changing the dark, black borders with darker versions of the colors that border is adjacent to. That way there isn’t super deep, dark, black borders distracting you from the art’s true colors. I’ve found this really helps with pixel art that has lots of bright colors.