This sentence can mean both " I wear a white coat" and " He wears a white coat" . The personal pronoun is often left out in the Japanese language and one must derive it from the context therefore I don't understand why was it a mistake to write " He wears a white coat ".
There are six colors which can be made into an い adjective by just adding an -い to the end the word. 白 (しろ) is one of these. い adjectives can directly modify their nouns by preceding them immediately. Therefore, 白い コート is correct.
Each time this makes me think of that one line from "They're Coming to Take Me Away."
Attempted translation: Ano yasashii otokotachi to karera no kireii shoroi kooto
Someone tell me how I did (even though I'm using romanji) please. I'm curious.