Yep, I ship RedxGreen over RedxYellow or BluexGreen...
Red and Green just seem to have chemistry there (in Green's first appearance, Red even claimed that Green was "his type of gal"). All the interaction between Green and Red is grand and interesting. Not to mention they both love to flirt with each other.
RedxYellow. I know there are shippers out there for these two but it just never stuck on for me... I don't know, Red clearly shows he doesn't see Yellow as a love interest, and the two barely even interact with each other. When they do, it's usually end up being awkward or plot based talk.
BluexGreen. Same reason as RedXYellow, they barely even interacted with each other.