五颜六色 (wǔ yán liù sè) is a set phrase meaning 'colorful, full of bright colors' — it describes a visual scene with many different colors. Unlike 彩色 (cǎi sè), which is a noun for 'color' (as opposed to black-and-white), 五颜六色 is a vivid descriptive phrase. It also differs from 丰富多彩 (fēng fù duō cǎi), which means 'rich and varied' and is used for abstract things like experiences or culture.