Specify the selection rectangle's color

Get a selection of the screen.
More information: <https://github.com/naelstrof/slop>.
Trick copyright: tl;dr; <https://github.com/tldr-pages/tldr>

slop -c {{red}},{{green}},{{blue}},{{alpha}}

click the source code to copy install slop on any operating system with command-not-found.com