颜 is a bound form (b.f.) that appears as a morpheme in many Chinese compounds. Its core meanings revolve around 'face' — both the literal face and its expressions (容颜, 笑颜) and the social concept of 'face' meaning prestige or dignity (颜面). It also carries the meaning of 'color' as in 颜色, which is the standard word for color. As a surname, 颜 is common (e.g., Confucius's disciple Yan Hui). Because it is a bound form, you'll almost never see it alone; it always combines with another character.