黑 pictures a person or vent blackened by fire and soot — the bottom four dots are the tell-tale flames (the same 灬 that cooks 热 and 煮). Black, in Chinese, is literally smoke-stained.
黑 darkens plenty: 黑色 (black), 天黑了 (it's gotten dark), 黑板 (blackboard). Modern slang made it sharper: 黑客 (hacker — 'black guest'), 拉黑 (to blacklist/block someone — the decisive end of a group-chat argument), 黑历史 ('dark history' — your embarrassing past photos). In opera masks, a black face means impartial and incorruptible — the judge Bao Zheng's iconic color. Not everything 黑 is bad.
A face smoked black over the fire 灬 — BLACK.
拉黑 'pull into the black(list)' — blocking someone on WeChat — is modern Chinese's cleanest breakup verb.