KColorChooser is a simple yet useful accessory application that allows users to click on an area of the screen and obtain the color value of that area of the screen represented in RGB, HEX, or HSV. It also allows saving a selected color from the screen to a color pallete. This tool is useful for web/app themers.
I don't think that there is similar application in the repository, but if there is it should be included anyway as a benefit to Plasma desktop users as they, like I do, may prefer a KDE/Qt based and as featurefull as other KDE applications when running Plasma.
GPL licensed FOSS