There were originally 6 channels on 27mhz. On higher quality sets you could use the gaps (in frequency) between two channels to get 6 or 7 more channels, Only later and higher end setups supported this.
I think there is so much 'slop' in the 27MHz Playmobil kit, that you need a full channel-width between channels.. So two adjacent 'straight' colours, or two adjacent 'splits' should be fine. - Just there is not enough discrimination in the RF to cope with a half-channel gap. YMMV of course..