蓝色(lán sè) - blue, the colour blue in Mandarin

蓝色 (lán sè) is blue. Like the other colour nouns it is built on 色, and it takes 的 before a noun: 蓝色的裙子, 蓝色的车. In the predicate the pattern is 是蓝色的.

Shades are made by putting a modifier in front of 蓝: 浅蓝色 is light blue, 深蓝色 is dark or navy blue, 天蓝色 is sky blue, 湖蓝 is a bright turquoise. 蓝 on its own works as an adjective in set phrases such as 蓝天 (blue sky) and 蓝领 (blue collar).

The trap is 绿 (lǜ, green). Classical Chinese used 青 (qīng) for a band covering blue, green and even black, and 青 survives in words like 青草 (green grass) and 青天 (blue sky). Modern Mandarin separates 蓝 and 绿 cleanly, but 青 turns up in older or literary text and will not tell you which one it means.