John Ronald Reuel Tolkien wrote his first story aged seven. It was about a "green great dragon." He showed it to his mother who told him that you absolutely couldn't have a green great dragon, and that it had to be a great green one instead. Tolkien was so disheartened that he never wrote another story for years. The reason for Tolkien's mistake, since you ask, is that adjectives in English absolutely have to be in this order: opinion, size, age, shape, colour, origin, material, purpose, noun. So you can have a lovely little old rectangular green French silver whittling knife. But if you mess with that word order in the slightest you'll sound like a maniac. It's an odd thing that every English speaker uses that list, but almost none of us could write it out. And as size comes before colour, green great dragons can't exist.
— The Elements of Eloquence: How to Turn the Perfect English Phrase
by Mark Forsyth