*thinks intensely* *talks "artistic" nonsense* Because there are so many colors for his one expression, it shows how he embraces his sexuality. The rainbow has been an icon for homosexuals for a long time, and this is Germany coming out of his prison, the closet! (Lol, seriously, no, I have NOTHING against homosexuals... IT was either that or the colors represented him doing drugs)
SHINE BRIGHT LIKE A DOITSU BISHIES!
//shot