They’re the same size and similar wood color.. I like that they’re different! I would paint the top of the one on the right black to match, add hardware to the one on the left and swap our the hardware on the left to match the new hardware like the one on the left.
You could also go crazy and paint the legs black too..
You could do some cool kind of baskets or cubbies in those open areas.. Do the same color or kind of basket/cubby and that will also tie it in.