In Castaway 2 what was the main pet that you used or what pets did you use? What level did you get them to? Also what level do you recommend your pet to be on before attempting more difficult areas in the game?

Loomis are the best

i stayed with the same pet all along the first one ;) just because i was too lazy to start leveling a new one again. but anyway i recommend anything poisonous!!

Loomis...they attack fast n give high damage

I think FireStarter is a good choice: missile, zone attack, melee, and a lot of HP. And it hatches with a good basic level...

Why do some eggs appear different color? I had a field snake egg that had green cracks on it, but when it hatched I didn't see anything on the stats to make it different from other eggs...

Each color of egg is related to an element:
Red : Fire
Blue : Ice
Green : Poison
Yellow : Thunder
Pink : Healing (Only Pixie)
White : No one
I think that's all.

Ok thanks, another thing - does the attack of each pet differ? So far I've seen only the usual melee as well as the eye thing that swoops down, but which one would be considered better?

There's no better, that's according to your envy. I have used the Pink Loomi (melee), the revenant, who create a poisoned area and swoops down, the Thunder Snake, who casts powerful lightning on enemy (but don't have enough HP), and now I've a FireStarter, who shoots missile, hit on a zone, and have a good amount of pdv. But I hold a good memory of Thunder Snake, that was fun ^^

So is Loomi the best pet? Or rather people say it is because they stick with it a long time and the pet levels like crazy so it's stronger.

Being a long time with the same pet help to make it stronger, but with an intensive training, any pet will be good. I think for example at the Forgotten Forge, where the Skill 'Miasma' give you glassful of Exp without make anything...
My pet (FireStarter) is level 38, and me too, but everyone have a favorite pet, and the strength of it is a relative notion.