I still say go for "gold." The reason? Some colors have certain meanings associated with them. Like...red is often used for "stop" or "warning" or "anger". Pink is usually associated with things like softness, women, love, calmness (police stations often had a "pink room" to place violent people as it has a calming effect). Green is associated with "go" and money. And GOLD has always been associated with things like royalty, money, pinnacle of achievement (gold trophies, gold medals, etc.).
SO...to make someone's name green or blue or purple...isn't going to have the impact or the "meaning" that the gold color would have. Gold is "special." Green is nice...its "planty" but if you use green, its going to look like someone just chose green to use as a color for their name. Its not going to look like its a "designation" for a premium member.
That's my 2-cents. I think the premium membership should be clearly defined.