This is a simple and highly scalable script, built with zenity (3.43.0) and bash (kbcol_ui.sh), manage Logitech's keyboard-LEDs (compatible models: G213, G410, G413, G512, G513, G610, G810, G815, G910, and GPRO). The most straightforward way I found possible was by using the dioni21/g810-led repo forked from MatMoul/g810-led as command-line led controller, associated with a clever idea from Nicholas Berlette at GithubGist to a simple RGB to HEX conversion.
Remember tt change the file permission to executable by sudo chmod +x <file_name>.sh, and it can be added to your $PATH at $HOME/.local/bin or /usr/local/bin/. Alternatively, if you want to cut everything and easily select a color for the whole keyboard, use the shorter_kbcol.sh script. It can be added to the $PATH as well or to a quick keyboard shortcut.