灰色 (huī sè) literally combines 灰 (huī), meaning 'ash' or 'soot', and 色 (sè), meaning 'color'. Together, it denotes the neutral, desaturated color gray — often evoking dullness, gloom, or natural ash tones. Unlike English 'gray'/'grey', which may carry stylistic spelling differences, 灰色 has no variant forms and is consistently written and pronounced as huī sè.

This word functions flexibly as both a noun ('the color gray') and an adjective ('gray-colored'), commonly describing physical objects (e.g., hair, clouds, concrete), emotional states (e.g., 灰色心情 — 'a gray mood', implying melancholy), or metaphorical ambiguity (e.g., 灰色地带 — 'a gray area'). It appears frequently in descriptions of animals (e.g., gray wolves, gray cats), weather, urban environments, and psychological nuance.