蓝

蓝 (lán) is the Chinese color word for blue — the color of the sky, the sea, and jeans. As a color adjective, it almost always combines with 色 (sè, 'color') to form 蓝色 (lán sè, 'the color blue / blue-colored'), which is what you actually use to describe an object: 蓝色的衣服 (blue clothes), not 蓝衣服. Bare 蓝 stays in compounds and proper names: 天蓝 (sky blue), 海蓝 (sea blue), 蓝牙 (Bluetooth, literally 'blue tooth').

Two notes for English speakers: first, Classical Chinese sometimes used 青 (qīng) to cover both blue and green, which is why you'll still see 青 for 'dark blue / blue-green' in poetry and place names. Second, the color does NOT carry the 'sad' connotation that 'blue' has in English — 'feeling blue' is 心情不好 (xīnqíng bù hǎo), never 蓝.