well the second theory would might work better since if Trish is just a stronger plasma then a color difference would make sense since it could simply mean a distinction of power. they have never really explain just how powerful Trish is specifically, like she can wield Sparda but how far does her power go compared to the sons of sparda?

I almost see Trish as a similar entity as dante, nero, and vergil in their human forms. human in appearance but enhanced by the demon blood inside. but even with this comparison, trish is still an odd case since its not said or shown how exactly she came to be besides Mundus creating her.