Count how many colors your XTerm actually supports, since it may be different from what tput colors reports.
For example, on my desktop (Ubuntu 11.10 with XTerm(271)) tput colors returns 8 while XTerm actually supports 256 colors.
./xterm-color-count.sh
You might have to wait a few seconds for the result to be returned.
./xterm-color-count.sh -v
Print each color number in its own formatting.
Gilles did all the research, and has awesome communication skills and *nix knowledge.