This is definitely worth exploring. Maybe combining directionality and interaction could designate the colors?
Combinations are:
RedFirst / RedFirst
RedFirst / BlackFirst
BlackFirst / BlackFirst
BlackFirst / RedFirst
If the first pair is Red its located at Loci Sub-Position A. If the second is also Red, the interaction stays at Position A. If the second is Black, the interaction crosses into Position B.
If the first pair is Black its located at Loci Sub-Position B. If the second is also Black, the interaction stays at Position B. If the second is Red, the interaction crosses into Position A.
So a practical example… Lets use Santa and Superman as our 2-block images that could represent either a red-first or black-first pair, drawn in that order.
The loci is a rocking chair. Sub-Position A is on top of the chair, Sub Position B is under the rockers.
If you get the Black/Black pairs, maybe Santa is tiny and running under the rocker and tackles Superman and they both fall to the ground and get squished by the rockers. This action starts at SubPosition B indicating black pair first and the action stays there indicating black pair also second.
Red/Black would mean Santa is sitting in the chair seat and is rocking back and forth, squishing Superman under the rockers. Action starts at Sub-Position A, so it starts with the Red pair. The action progresses to Position B, so the second pair is the Black version.
Red/Red would both be in Sub-Position A, so maybe Santa is sitting in the chair, then Superman comes by and sits on his lap.
Black/Red would be B to A… So Santa starts under the rollers and maybe pushes them up and off him, flipping Superman violently out of the seat where he was sitting.
If you are partial to detailed memory palaces this approach could work really well. You could pre-plan the sub-positions, and even pre-plan some of the interactions across them…