The Pied cockatiel is the first mutation of cockatiel colour genetics, with a mostly grey to light-yellow and white feathers and orange cheek patches.
Pied cockatiels have large, random blotches of colour on their bodies, after the "normal grey" or "wild type" of a cockatiel's plumage is primarily grey with prominent white flashes on the outer edges of each wing.
Bird breeders can breed for certain traits, and they have been breeding for different colour mutations in cockatiels since the 1940s.[1]
There are two kinds of pied cockatiel colour mutation in this mutation,"Heavy Pied cockatiels" and "Light Pied cockatiels".
the difference between Heavy Pied cockatiel and Light Pied cockatiels, a Light Pied cockatiel should have 10% pied colour (any less and they could indeed be split pied) and a Heavy Pied cockatiel should have more than 75% pied colour. there are many variations of pieds from just a few pied flights and body feathers to a bird that is predominately yellow (or white) with just a few dark feathers, which is sometimes referred to as a "reverse" or "saddleback" pied.
if a pied has no dark feathers or 1-2 dark feathers on the face, chest or rump it is referred to as a "clear pied". Clear pieds can often be mistaken for a lutino, the difference between a clear pied and lutino is in their eyes. Lutino's eyes will reflect light back red in both the pupil and the iris, a clear pied will have black pupil and brown iris (if the bird is also cinnamon the pupil will be wine colour while the iris remains brown)