When the golden age will be here again with the 3D printing of the joy caps, I think I will try different colors, too.
The favorite one will be the green probably, but that will be cool, as well, when there will be EPs on the table with joy caps of different colors. Red (like stop key), blue (like function keys) or further, what you can imagine, like yelow, and such. I could distinguish my EPs with a quick look ... green joy cap is the EP what with I use often, red joy cap is an extended or overclocked one, blue joy cap is an EP with a perfect nick, et cetera.
They will have characteristics from the joy cap color. Exciting times come.