I believe (from when I was involved in actively tracking them) that the SRT6 colors from most sold to least sold were:
1. Black
2. Aero Blue
3. Sapphire Silver Blue
4. Gray
5. Apparently there are 1 or 2 Machine Gray ones out there as well. Seems like someone on here has one.

The other folks are correct, Chrysler nor Karmann have given us any data other than 2,016 SRT6 Coupes and 928 SRT6 Roadsters were made in total. Some of us on here started tracking all SRT6s we could find and creating our own database. Crossfirefun now holds all of that data.

Cheers.