Super Saiyan 6 is just an upgrade of the Super Saiyan 5's appearance and power. The silver color of the Super Saiyan 5's hair and fur is upgraded to a gold color, in a similar manner to the base Super Saiyan form. The hair and tail is lengthened as well, giving an appearance similar to a Super Saiyan 5. The reddish-brown skin pigment that a Super Saiyan 5 possesses is glorified, brightened, and lightened to a light tan color. However, the user's eye color stays the same color as Super Saiyan 5, unlike the rest of the transformation characteristics, and the eyes are lined with a red color. Super Saiyan 6 deepens the voice of the Super Saiyan 5 even more.
http://dragonballaffanon.wikia.com/wiki/Super_Saiyan_6