If the crayon.colors option is set, then we
just use that. It should be an integer number. You can use this
option as a workaround if crayon does not detect the number of
colors accurately.In Emacs, we report eight colors.
Otherwise, we use the tput shell command to detect the
number of colors. If tput is not available,
but we think that the terminal supports colors, then
eigth colors are assumed.
If tput returns 8, but TERM is xterm, we return 256, as most xterm
compatible terminals in fact do support 256 colors.
There is some discussion about this here:
https://github.com/gaborcsardi/crayon/issues/17
For efficiency, num_colors caches its result. To
re-check the number of colors, set the forget argument to
TRUE.