Anyone wanting to try the color selector build from @rodlie on Linux,
here you get the compiled version to download (only shortly tested on PopOS! 20.04 LTS).
In this build, you can create a color palate in the ColorCorrector node with hitting the Add button (or Shift+A). You clear a color with right-click (or all with the “Clear” button (or Shift+C)).
Big thanks to @rodlie 
