I know that Green is carried and blue is a vis but I've been seeing purple on most pets either from breeding or the themed pets but what is it? Is it a hidden trait or is it something else?

purple traits are often called hiden or ressessive traits, it mean that bellow the visible trait in that slot is also a carried trait. You can know what the hiden trait is by looking at the letters in front of the name of the trait. By exemple in the case of this ny'vern :

Gene One: (FJ) Crested Lizard
Gene Two: (NN) None
Gene Three: (NN) None
Mutation One: (NN) None
Mutation Two: (NN) None
Mutation Three: (II) Flowered Wing Wrap

G1 have a ressessive, the F in first the first part of the genetic is the letter for crested lizard but instead of being followed by a second F in the carried slot, like it would be normaly the case, the carried is marked as J witch is Diamondback. This mean that there is a chance for an offspring of this pet to get Diamondback as a visible instead of Crested Lizard. ^-^

Purple means there is a hidden trait under the vis.

Example:

Mutation Three: (DE) Ice Crown

On this Vulnyx, D represents the trait for Ice Crown. If it were (DD) the trait would be blue. As it is, it's purple because the (E) represents Lucky Dust.

Think of punnet squares. Parent A has (EE), Parent B has (DD). The child will be (DE) as it inherits one value from each parent. In Sylestia the dominant trait is the letter closest to A - so D trait will be visible rather than E, but the E still has a chance to be passed on when breeding.

Thank you that has been confusing me for awhile now,