Pick any color on the screen and have the hexadecimal representation insert into the currently active editor. This is a thin wrapper around the xcolor program.
Once you have an editor open, you can trigger the Pick screen color
command. You should see a small preview window attached to your cursor, once
you selected a color, the hexcode will be inserted at the current position of
the cursor.
This extension requires you to have xcolor installed globally. See
https://github.com/Soft/xcolor for installation instructions.
Note that xcolor only supports linux systems running X11.