Have teams ship two robots: One painted red and one painted blue.
The only problem I see with the flags is the fact that they fall out. The previous suggestion of using a rubber stopper or something of that sort would work except for the fact that we have yellow flags now. Both have to be able to fit.
Maybe, instead of something like that, the standard flag holder could be changed to include short peices of surgical tubing attached (with screws or zipties?) in such a manner where both flags will fit, and they will be somewhat secured.