Great ideaCathy79. Did you notice how much darker isi's was to JulieO's (mine looked like JulieO's) so if you could get one batch of each colour,the contrast would be fairly marked. Or make one layer a plain vanilla flavoured 'cream', leaving out either the coffee or the chocolate. Or (oh the possibilities are endless) use white chocolate in one batch and dark choc in the other.
Good ideas cathy79 - would be good to have different textures too.