KColorChooser is a handy little tool for picking colors anywhere on the screen. For instance you might want to know what color the menu is on a website or maybe the color of an icon in the application launcher.
To install KColorChooser on Kubuntu 20.04 open Konsole and type,
sudo apt install kcolorchooser
After installation you can find the application in the application launcher under Applications/Graphics/KColorChooser.