Full-colour mode

[maandree]

\e[38;2;${red};${green}${blue}m and \e[48;2;${red};${green}${blue}m can be used in xterm-compatible terminal emulators for 24-colour. Some terminals, including xterm itself, will match to the closes colour in the 256-colours colour palette.

[charc0al]

Since this issue is still open, I'll point you to my cowsay file image converter which does much the same thing, and supports full 24-bit RGB color (and also gives you nice pretty-printed cow files that are human readable)