OK, that's neat 
So far we've had dancing penguins and loops of colored cloth on rolls. Any other ideas for a low-res display?
A bunch of fans sitting in specific seats in a stadium each holding different color cards. They raise different color card on cue. That is low res but done in many different kind of stadium games.
While this is common in modern day football (and other) games, I wonder had the Romans tried that. Pure congesture on my part. Imagine: Caligula makes certain signal, and the fans in the Colosseum raise purple cards together display a dot matrix word saying (in Latin, of course) "Good Horse Makes Better Senators."