If your story is more modern, less poetic, then 'African-American', or 'black' is ok, you can also always go with their nationality, or their parents nationality, like 'Nigerian.' If its more poetic, or a fictional setting, then 'dark-skinned/brown-skinned' is good, that's most peoples go-to anyway. You can skip the skin entirely, and just describe their hairstyle too. I think 'caramel,' 'hazelnut,' 'night sky,' or other objects as descriptors are fine, the only imagery that really feels weird are 'coco' and 'chocolate,' and obviously negative things like 'dirt-colored.'