And again, forgive me, but I don't understand your argument Aestu.
The argument is simple. The fun factor of real-life exclusives is undermined by making the items have an impact on game balance.
If Leeta were purple, her exclusive combination of traits in a purple doff would have an impact on game balance. Players who do not have Leeta would be at a disadvantage and feel compelled to get her. The doff would become a power consideration rather than purely a novelty.
Novelties are most fun when obtained incidentally and not because one feels compelled to, and players who don't have them don't feel disadvantaged. Therefore, Leeta should be blue, so she is merely a novelty, and the fun factor is not undermined by game balance.
Since I have one, of course I am hoping it becomes purple. For myself. =)
From the pov of considering the game as a whole, though, I think it should stay blue.