The everyday compound is
黝黑 (deep dark / sun-tanned dark) — the only place most learners will meet
黝. It typically describes either (1) a deeply tanned, weathered complexion (
皮肤黝黑), often with positive connotations of healthy outdoor labour; or (2) physical darkness — deep night, dense forest, a glossy black object. Avoid using
黝黑 of a person's natural skin tone in a way that sounds judgemental — it's neutral-to-positive when describing weathered toughness, but can read as rude in other contexts.