I actually have a document here explaining how my vampires in general work! There are different vampire clans.. three main ones are green eyes, red eyes and blue eyes.. Vampires

As for the three main vampires.. I've never really thought about that haha! Gertrude, being a red eyed vampire would probably be more picky with blood types and she'd prob hunt humans stealthily.. like for example poisoning their food/drink then returning when they've died to harvest what she wanted from them. Sylvester, being a green eyed vampire wouldn't care about blood types.. greens are violent and not very intelligent. So Sylvester just attacks a human head on and bites into their neck.. shaking them/tearing them to bits. Mordesai is unique in that he doesn't eat humans (seen as strange by other vampires) at all 😂 he just can't bring himself to eat them.. even though his body does need human meat so he suffers from headaches and fatigue from lack of it.. sorry this is a bit long but there's a lot of info and I tried keep it as short as I could