I think you could increase general MC spent on a daily basis, in between your marquee themed sales. Impulse sales are addictive! Being able to pickup 3 colors for 750 MC is worth it to those of us that vote with our wallets. Micro-transactions work best when there is something someone wants to buy.
It can be frustrating having to wait months for a sale on the colors, I most want to use.
-or- lower the overall MC cost of non-premium colors!
