This is my proposal for the new colors of the Year Member distinction and I based it (somewhat) on the colors of award ribbons and World of Warcraft weapon and armor tiers.
1 Year Member - Grey
2 Year Member - Brown
3 Year Member - Yellow
4 Year Member - Orange
5 Year Member - Green (a darker shade of green than the current one)
6 Year Member - Red
7 Year Member - Blue
8 Year Member - Turquoise
9 Year Member - Purple
10 Year Member - Sparkly Gold