蓝is a noun\adjective，means the color blue, 蓝色 is a noun too, means blue color, 蓝的 is an adjective, means blue. "n. +的= adj. " is a structure. so you may say 我有蓝色的衬衫（I have blue shirts），我有*件*蓝衬衫(I have a blue shirt)，我的衬衫是蓝(色)的(my shirt is blue). hope it helps ;p

我有蓝衬衫 = 我有蓝的衬衫 = 我有蓝色衬衫（写成“蓝色的衬衫”会更好）。

Thank you both. In a sentence, for example : 我有衬衫 Which one would I use ? Can I say 我有蓝衬衫 as well as 我有蓝的衬衫 or 我有蓝色衬衫 ? Does it mean the same thing ? Thanks !

我可以这样说： 天很蓝 天是蓝的 天是蓝色的

ok, 蓝 is a noun, and 蓝色 is a adjectival & noun one , and the 蓝的 is a adjective ... for example ,when i ask the color of your shirt , you can answer 蓝色 or 蓝的. and we say there is seven kind of color, 红橙黄绿蓝靛紫... so can you understand?