Slate is a color-adding factor similar to grey and violet. Slate produces a very dark bluish grey in white-based budgies. The darkness of the slate varies slightly according to the dark factor of the bird. Slate, like violet, can be present in a green (yellow-based) budgie, but only produces a darkening effect. True slate only appears on blue (white-based) budgies. This variety is extremely rare.

Basic Genetics:
Sex-linked (on the x-chromosome)

For more info on slate budgerigars and their genetics, see Slates by Deamonn A Mullee

photo courtesy of and copyright Didier Mervilde	photo courtesy of Ghalib Al-Nasser
The slate variety has a very dark grey-blue body color.