All budgies have a level of "dark factor" ranging from no dark factor, one dark factor, or two dark factors. Wild budgies have no dark factor. Dark factor basically darkens the blue in the body feathers. (In budgies totally lacking normally colored feathers, such as albinos and lutinos, the budgie's dark factor will be present but unknown). A green (yellow-based) budgie with no dark factor will be the original very bright green; this variety is called "green" or "light green." One dark factor will result in a darker green; this variety is called "dark green." Two dark factors will result in a deep olive drab green color; this variety is called "olive." A blue (white-based) budgie with no dark factor will be the original bright sky blue; this variety is called "sky blue." One dark factor will result in a slightly darker blue; this variety is called "cobalt." Two dark factors will result in a deep grey blueish color (more grey than blue); this variety is called "mauve." Within each level of dark factor is room for some variation in darkness. One sky blue may look a little darker than another sky blue and one olive budgie may look a little lighter than another olive budgie. But usually there is no mistaking which dark factor category a budgie falls into, and the pictures below can be used as a guide.

Basic Genetics:
Dark factor - semi-dominant
Normal - recessive
Details on dark factor genetics...

No dark factor in a green (yellow-based) budgie relults in the classic light green variety.	One dark factor in a green (yellow-based) budgie relults in the dark green variety.	Two dark factors in a green (yellow-based) budgie relults in the olive variety.

No dark factor in a blue (white-based) budgie results in the sky blue variety.	One dark factor in a blue (white-based) budgie results in the cobalt variety.	Two dark factors in a blue (white-based) budgie results in the mauve variety.