c.1300, from O.Fr. orenge (12c.), from M.L. pomum de orenge, from It. arancia, originally narancia (Venetian naranza), alteration of Arabic naranj, from Pers. narang, from Skt. naranga-s "orange tree," of uncertain origin. Loss of initial n- probably due to confusion with definite article (e.g. une narange, una narancia), but perhaps influenced by Fr. or "gold." ... Not used as the name of a color until 1540s.
I am really interested in more details on why 'orange' (fruit) was chosen to represent the color. Also, if there are sources that systematically deal with names of colors in different languages or changes over time that would be very interesting, too. Colors are an example of a very stable (static) concept with corresponding terms ('main' colors) for which throughout history there had been a need (more or less important) to have words for.
Bonus question is — what was orange called before 1540s in English?