The Budgerigar, usually called Budgie, is a common wild small parrot throughout most of Australia, including the arid inland. It is also a common pet/aviary bird worldwide.
The natural plumage is green front/body with yellow face/head and dark grey/black barring with "scalloped" black wing feathers edged in pale yellow (similar to the bird on the far right).
Many other colours have been bred in captivity. The male has a blue "cere" (nostrils) and the female has a pink or horn-coloured cere.
Three's a crowd. Captive bred birds, particularly show birds, are much larger than wild birds.
Bright green is a popular aviculture colouring, usually retaining the yellow face and dark scalloping of the natural plumage - close to the wild colouring.
Various blues, often with a white face and crown, are another favourite.
Turquoise blue is one on the most popular colours, usually with a white face
but sometimes with pale yellow.
Canary yellow is another of the most popular colours, either retaining the black barring/scalloping
or sometimes pure yellow without barring.
Other colours include white
(this one with a pale blue back and some grey mottling),
and even pink and brown.