Probably galactic! I have a bunch that are galactic already, it's such a good color. And it can fit all my characters, either they are in space or they have gorgeous intricate gold designs.
For a while I thought I'd end up having nothing but Nostalgic pets, so that would definitely work for me!
Aqua or cream are definitely both my favorite solely color scheme skins.
[img align=center]http://31.media.tumblr.com/tumblr_lpegiz0BxB1qdy4fko8_400.gif[/img]
Probably either Glacier or reborn.
Oh mannn, that's... a really hard question, because I have 62 pets and my characters have some variety with design+personality. My favorite color is sweetheart so my initial impulse is to say that, but, omg, the idea of Halden being sweetheart is.. wow haha.
I think I'd probably end up going with either a colorfill (sun or cream, maybe?) or galactic! Galactic has a pretty good variety of personalities and it's not overtly stereotypically feminine or masculine. Reborn would also ALMOST work, except I have one character who explicitly has ice abilities, and that would be a bit awkward haha
All I know for sure is that I'd probably have to change a lot of pet species since I have, like, 10 hipottus and a bunch of bhakorus and telenines and ontras.

[flower=lea]
I have way too many pets with tons of different personalities, so that's really hard to say.
I'm leaning towards Reborn because I could probably find suitable matches for a lot of them in that color. Bloodred has a lot of applications, too, it'd just be focusing on specific sides of characters rather than what they specifically /are/ or what they come off as. You know?
And if "Common Experiment" counts as a color, I could be totally up for that too.
That's actually a really difficult question to answer... My first impulse is to say Angel or Nightmare, or even Glade. But..I like the most different species of Bloodred, and Chibi than anything else. I love all the Angels, too... But all my pets have their own characters, and Angel definitely does NOT fit the majority. So strictly color appeal, I'd say Angel, but otherwise I'd probably have to go with Bloodred.
Common might sound boring, but I like having variety. I'll like Nostalgic or Chibi too.
[IMG]https://img.pokemondb.net/sprites/black-white/anim/normal/staraptor-f.gif[/IMG][flower=EagleWing]
hmm probably blacklight, glade or storm
GLADE is the best !!
[tot=honor]
Patience. I colored patience gray, hung over with black clouds. I colored hope yellow, just like the sun we could see for a few short morning hours. Too soon the sun rose high in the sky & disappeared from view, leaving us bereft and staring at blue. 🌻
One colour, mm that's a tough choice. I suppose I'd go with either Bloodred, Reborn, or some colour-fill. A good portion of my characters are vampires, so that's where the Bloodred fits in. Though, currently, my only Bloodred pet isn't a vampire at all lol

I don't think I could pick just ONE colour for everyone. Pet colours are something I think very carefully about, as well as species, and I love soooo many of them! ^-^ I look through everything available to find something suitable, whether it's for a fan pet, an OC, or a pet that just has a nice word for a name. c:
If I HAD to pick, I would probably go with something as neutral as possible, like Common. Overlays would take care of getting the personalities right.
I would leave them all common - unless I had to pick a color... lol. then I guess, um... Arid c:
Angelic! I just love the colors and the serene look of all the pets. Well, almost all... that Mortiking... >_>;
Galactic or Storm. I have SO many pets that are space-themed or at least space-related, I could make it work. Storm cause I love lightning and I waited 9 years for a color like that.