Purple is in the works, production will start in the near future on SRT8's and R/T Classics (which have the choice of black or white stripes!). Unfortunately the window for ordering this limited edition color has ended, or will end December 23rd, depending on what source you hear it from.
You'll start seeing the purple Challengers in late winter or early spring.
There was already a thread on this here:
https://board.moparts.org/ubbthreads/show...;gonew=1#UNREADGreen is strongly rumored to be the next limited edition color release. It hasn't been officially announced but I expect you'll see that color as a late 2010 limited edition, or an early 2011 color, if Chrysler survives that long!