I see a lot of people having pets with slightly altered colours in their art, but the lines and everything else aren't changed... is this a custom overlay, or is this something I don't know about? Sorry about the stupid question, I'm a bit new here. ^^"

Most likely it's just an image touched up and uploaded in place of the default. Can you give me an example of what you're talking about? :)

It it's a custom overlay, before the pet species and color, it will say "custom." For example, Name the M Custom Glacier Kumos.

http://subeta.net/pets/Kittera

That's an example I found, I was a bit confused because it didn't say anything about a custom but it was differently coloured.

If the altered image is only visible on the pet profile itself then it's a normal overlay that has been put over the original image with coding - example would be my Pet Morpheus who is shown in purple on his pet profile but is actually still the original blue Angelic Lasirus everywhere else on site.

A custom overlay on the other hand show for everyone everywhere (pet profile, user profile, pet leash, user info hover etc.) on site, an example would be my Custom Reborn Legeica Haggard.

Ah, I see! Thank you for explaining, that helps a lot :)

You are welcome, glad I was able to help c: