I try to have consistent colour coding across my DNA analysis, a lot of which I do in a spreadsheet, but I also use the same colours for my Ancestry dots. I use 4 colours for my great grandparent pairs - Blue for my paternal grandfather's parents, Green for my paternal grandmother's parents, Yellow for my maternal grandfather's parents and Pink for my maternal grandmother's parents. If I want to split matches beyond that I use darker shades of those colours (tones of navy, bottle green, orange and red). If I'm dealing with someone closer eg 1C or 1C1R I duplicate them eg a paternal 1st cousin is blue and green. Hope that makes sense! As you say I don't need to colour on Wikitree.