Helpful for configuring terminal program colorscheme, like vim,tmux,bash,zsh,etc.
Note that if color 0~15 was changed in terminal by configuration file or
CLI option, the corresponding hex & RGB value will be shown falsely.
Usage:
./show256color [option]
without option,show 256color in background.
options:
[b|-b|bg|-bg|--background] show 256color in background(default)
[f|-f|fg|-fg|--foregroung] show 256color in foreground
[x|-x|hex|--hex] also show color value in hexadecimal
[r|-r|rgb|--rgb] also show color value in RGB
[h|-h|help|--help] show the help