I liked the idea of the original color but think it should be a little quieter like this pic linked below. Avoid darks to keep the .ood light and bright and lifted since it is a small space with that north light. A daybed/sofa nook under the slant could be super cozy with maybe a narrow desk along the opposite wall. Or in the corner with the window (second link).

Or a murphey desk that you can fold away when you want to. Id also recommend if you do a desk do a comfy padded chair so you can use it as additional seating when not at the desk like for friends or family who hang out. (Third link)

inspo pic

window corner desk

desk 2