暗色 is the opposite of
亮色 (liàngsè, bright color). For UI/dark mode you'll see
暗色模式 (ànsè móshì) on Chinese apps. Note
暗 (dark) versus
深 (shēn, deep) —
深色 (shēnsè, deep color) is more common for things like navy or burgundy;
暗色 leans toward dim or shadowy.