THE DOMINANT MUTATIONS
The Zebra Finch Dominant mutations comprise Greys, Dilute Blues, Silvers, Creams, Black Faced, Black Bodied, and Crested. The dictionary shows that “Dominant” means prevailing or controlling – for example, capable of exerting a prevailing or controlling influence. If we relate these meanings to our Zebras it is obvious that  a Dominant character parent would have a prevailing or controlling influence on the colour of its young birds.
In theory the Dominant mutations should be the easiest of all to breed, for a healthy bird of Dominant character is capable of producing birds of its own particular colouration (in its first mating) regardless of the colour of its mate. When a pure Grey is mated to another Dominant character bird, young birds of each of these varieties can be produced, but NONE of those young Greys can be split for the colour of the other parent because IT IS NOT POSSIBLE FOR A BIRD TO CARRY HIDDEN GENES FOR ANOTHER DOMINANT COLOUR FORM. What you see is what you get. The colour (or markings) of the bird indicate what the bird actually is. If one bird of a mated pair is of a Dominant variety there SHOULD ALWAYS  be a percentage of young of that Dominant variety in their nests. One variation of this rule is the Cream, which must be mated to Cream or Fawn (or in the case of a Cream hen– a cock split to Fawn) to produce Creams of both sexes.
If a Black Faced Grey cock is mated to a Grey hen, or a Grey cock to a Black Faced Grey hen, you will often find in their nests some young Greys which are not Black Faced. The  young Greys will be pure Greys. It makes no difference which of the parents is the Black Faced bird.
However it is possible for a bird of a Dominant variety to be split for a Recessive  colour form, also  a cock of a Dominant variety can be split for a Sex-Linked colour form.