Almost same, but slightly different. OK:青い海 NG:青の海 Blue is one of the natures of the sea OK:青の洞窟 OK?:青い洞窟 Blue is not one of the natures of the cave. Probably the blue of water is reflected in the cave, it looks blue, and people named it "青の洞窟" OK: 赤の魔術師：Magician of Red. He probably utilizes red color in his magic effectively. OK: 赤い魔術師：Red magician (actually his color is Red) OK：茶色い車 OK：茶色の車 OK：赤い車 OK：赤色の車 OK：黄色い車 OK：黄色の車 Brown/Red/Yellow is one of the natures of the car? The answer can be yes and no both. Then 黄色い/黄色の both are OK. ※ The word 茶色い is a little bit strange to me , a native speaker. 茶色(brown color) is a noun. How come you can make it into ajective ”茶色い"、by adding "い"？ I don't know other words with same structure except for slangs such as "ナウい”(NOWい),".

茶色の車です and 茶色い車 are both correct sentences. 茶色 modifies 車 different ways in those sentences because the first茶色 and the latter 茶色い belong to the different word classes. i.e. 茶色 is noun and 茶色い is adjective.

Hi,I think both of them are correct. I'm afraid that I can't explain the difference. it's totally same!