Big thanks to both the Dans. The breakdown of writing out the possible pairs of mauve dinos for sure helps and far more manageable–and effective in my opinion than 7sage’s approach. I guess I wasn’t very direct with my statement, but I when diagramming the game, I wrote out the conditional rule u->~v correctly, but I didn’t take the next step to see that it means that at least one of them must be out. I need to get more comfortable with the rules to see that, I guess.
Thanks again guys.