> Medieval scholars inherited the idea from ancient times that there were seven primary colours: white, yellow, red, green, blue, purple, and black. These corr

> Medieval scholars inherited the idea from ancient times that there were seven primary colours: white, yellow, red, green, blue, purple, and black. These correspond to the classic tinctures of heraldry: the "metals" or and argent (silver and gold, conventionally depicted as white and yellow), and the "colours" gules (red), vert (green), azure (blue), purpure (purple), and sable (black). However, iirc, purpure as a colour in its own right was a later addition, and was originally just considered a variant of gules (mediaeval heraldry lacking Pantone numbers or rgb/cmyk specs -- as long as the chosen paint or fabric was recognisably green or yellow or whatever, it counted). > Finally, yellow or gold knights were rare and blue knights nonexistent. The nearest thing to a canonical version of the Arthurian romances in English is probably Sir Thomas Malory's Le Morte d'Arthur, which may be too late (c. 1470) to count as strictly mediaeval, but which does include a single example of a blue knight: > So leave we Sir Gareth there with Sir Gringamore and his sisters, and turn we unto King Arthur, that at the next feast of Pentecost held his feast; and there came the Green Knight with fifty knights, and yielded them all unto King Arthur. And so there came the Red Knight his brother, and yielded him to King Arthur, and three score knights with him. Also there came the Blue Knight, brother to them, with an hundred knights, and yielded them unto King Arthur; and the Green Knight’s name was Pertolepe, and the Red Knight’s name was Perimones, and the Blue Knight’s name was Sir Persant of Inde[0]. -- Le Morte d'Arthur, book VII, chapter xxiii. This same part of the Morte also features (briefly) a brown knight, a colour not discussed in the article. [0] inde: dark blue; etymologically related to "indigo", both words being ultimately derived from the Latin indicum.