Cockatiels

Cockatiels come in various colorings called Pied, Pearl, Fawn, Lutino, Albino, and Gray. The colors are made up of of whites, yellows, and grays. Oh and most of them have a little splash of orange on their cheeks ;) I have done a typical gray cockatiel, and a lutino(white with yellow) cockatiel design below, as these are 2 of the birds I personally had in my life!

 

Parakeets

Parakeets, or Budgies, come in so many different colors. Predominantly you'll find them with either a green/yellow or a blue/white color scheme.
The first pet bird I had was a parakeet named Polly, and he was the standard green parakeet! My love for parrots really started with him, and over the years my family had a few different ones. Below are designs inspired by the ones we've had over the years:

This is an English Budgie. They're a bit larger than a normal parakeet.