Sorry no. Actually, quite a bit goes into those theme colors, making sure the accents work well on other apps, with light or dark backgrounds. So unfortunately Microsoft.has limited the selection.
Before installing pre-Mango, I was dev unlocked and was able to change one of my colors to Dark Red, which looked really good. I lost lost the ability to add colors after Microsoft removed the app with pre-Mango, and then lost the color when I hard reset just before installing Mango. I miss it, but I have gotten over it.
Sent from my HTC Surround using Board Express