That being said, I've successfully collected all the colors of the lizard/lizard models! Not only that, they're all rare quality. :D
Left column, top to bottom: Lizard Hatchling, Twilight Iguana, Spiny Lizard
Right column, top to bottom: Spiky Lizard, Horny Toad, Ash Lizard
Originally, I was hoping that some of these pets would be color-changers so I wouldn't have to collect specific ones, but it turned out that they didn't have that special color switching quality.
So I had to go out and find one of every color. But I wasn't satisfied with just unique color; they had to be rare quality too.
I think that was the ultimate challenge. It's quite easy to go out and find a pet that has a certain skin, but to find a companion in that color AND specific quality? The RNG odds are definitely stacked against you. Not only do you have to first track that companion down, the color and quality that it spawns with is completely randomized.
I had to make a list of which lizards I wanted in what color. Unfortunately, some of them only come in one or two skins, while others can come in more. Coordinating which color should go with which specific pet made it slightly easier figuring out priorities, but it was still a challenge to find those companions that matched my specifications.
This meant a lot of time terrorizing Orgimmar's critter population in search of just the right Spiny Lizard. I went through so many of them that I lost count after the first hour. It was a good way to earn some easy experience for some of my lower level pets, though.
Each one picture above is a unique pet, same model, different color. I was tempted to try and capture duplicates in different colors, but I needed to collect one of each unique companion, anyway. Got two birds with one stone for this one.
In the end, it took me all night of hunting and traveling from zone to zone to find just the right ones. But now my lizard collection is complete! I couldn't be happier or proud. :)