I have just read a post in one forum and a guy said that “we can not see any colour even with a giant scope”. But I doubt if it is true or not. Some veteran observers say that it is possible to see nebula colour through huge scopes, even small scopes. One guy claimed that the M42 that he saw was greenish.
But I feel confused at this moment. As a student who studying Biology, I have a concept that we can’t see things with colour.