I handle the multiple Sketchup versions conundrum by editing the icon under Get Info.
Select the app in the finder, hit Command I to get info, select the icon in the upper left with a single click (blue shading will appear around it) then paste in whatever you want. I copy the old one, paste it into a graphic editor, change the color, copy it again, and paste it back into to the Get Info window, instant version colors! You could write the year across the icon if you wanted.
I think I’ll make 2020 green.
