c256 will tell you if your terminal supports 256 colors. It can also be used to list the actual hexadecimal RGB values of each mapped color.
c256 [-c columns] [OPTIONS]
OPTIONS
-s, --square square format (default)
-l, --list list format
-c, --col n columns
--hex show hexadecimal values of each color
-h --help help message
-m --man view manpage
TRIVIA
The background notation to use is <ESC>38;5 - \033[38;5;100m
The foreground notation to use is <ESC>48;5 - \033[48;5;197m
AUTHOR
Written by Magnus Woldrich