So I just did all of these and had a it all done, then my browser closed. >.< Doh. So, starting over...Hmm, I swear I had more the first time around..oh well. :/
Anyway. I know you said 'colour > species > character personality', but I am a hardcore Harry Potter fan, so when I was picking things out, the personalities/general character started to win out over color...but I tried to reel myself in, I really did. But I kinda failed. Oh well?
Good choice for wormtail, and my general idea when picking out petpets for him was that he was a weak spineless little ..well a word I cannot use here. He's not like 'I'm gonna beat you up' evil, but 'I'm going to sell you out because I can' evil. Which is worse, but anyway.
Without going for the obvious werelupe, I like these two for Lupin best. No preference really, both are good choices. Anyway, when picking out these petpets, I started think about how studious he is and how withdrawn he was without Sirius and James. The ghost petpets are because I was thinking about how much time he spent in the shrieking shack and how people thought it was haunted.
As you can tell, I did not over think these matches at all.
With Sirius I tried to match things that had the same fun personality as he had, he was very loyal and fun loving, ready for a fight and I always imagine him stealing from Filch. So yeah, that's where these came from.
I understand your not wanting too many lupes, but the shadow lupe nails him perfect.
and oh, all wizards love owls..
And as for James..well I guess it would be in bad taste to make him a ghost pet, eh? Hmm, the only manly looking ixi I can think of is the tyrannian ixi...but that's not very stag like. I don't know.