The following command picks a color on screen (only way I found to be working on Debian sid / Wayland/Gnome 42.1) :
gdbus call --session --dest org.gnome.Shell.Screenshot --object-path /org/gnome/Shell/Screenshot --method org.gnome.Shell.Screenshot.PickColor
But the output is
({'color': <(0.094117647058823528, 0.10196078431372549, 0.10588235294117647)>},)
What is the color model here and how I can convert it to rgb or html colors ?