Peruse the available paint brush colour options for each species of Neopet. (It's our own version of the Neopets Rainbow Pool.) You can even see a list of which ones haven't been released yet!
The following biology parts can be removed with the appropriate Be-Gone! can (not applicable to Pet Styles).
Prior to April 2007's big revamp, Neopet colour combos were available in static poses, which you can see below:
Circle
Faded Circle
Happy
Sad
Angry
Sick
Petpage Photo
Close Attack, Left
Close Attack, Right
Ranged Attack, Left
Ranged Attack, Right
Defended, Left
Defended, Right
Hit, Left
Hit, Right
This Neopet was not available in Unconverted (UC) form prior to Pet Styles being released.