I can strip off some of the mystique in crosses of this type, but it will take a few minutes to go through some genetics. Keep in mind that there are lots of modifier genes involved so there will be plenty of variation not described below. As an example, a green egg layer crossed to a green egg layer can produce a pale almost grass green egg layer due to modifier genes.
First, define egg colors
White - common in games and others
Zinc White - bright white eggs, common in Leghorns
Tan - common in Wyandottes and other nominally brown egg laying breeds
Brown - Any of the Rocks or other brown egg laying breeds
Dark Brown - Marans and others selected for intense brown porphyrin coating
Blue - OOcyanin gene on chromosome 1 combined with genes for white eggs
Sky Blue - Oocyanin on chromosome 1 combined with Zinc White
Tinted Blue - cross of a brown layer and a Sky Blue layer gives light tan over blue
Green - cross between a brown egg layer and a white egg layer will produce this
Olive Green - cross a blue layer and a dark brown layer may produce this.
Porphryin (brown coating) production is a biopath, not a gene. There are at least 13 documented genes involved in porphyrin production. All chickens have the porphyrin biopath. Some chickens have one or more genes in the porphyrin biopath disabled which results in eggs that have no brown coating. In other words, a Leghorn has the genes to produce porphryin, but because one or more genes are disabled, a Leghorn produces white eggs. Some of the porphryin genes are sex linked, but to my knowledge this has not been documented in a peer reviewed paper. In some crosses, there will be a difference determined by which parent is male and which female. For most very dark egg layers, parent sex does not appear to matter.
Zinc White has the effect of almost entirely negating production of porphyrin in any cross where it is present. I am not certain if Cream Legbars carry the zinc white gene, but if they do, even crossing to a very dark brown egg laying line of Marans will wind up with less tint on the eggs.
Would a picture help? These eggs are from a cross of Silver Laced Wyandottes with blue egg laying Brown Leghorns. They have Oocyanin for blue, Zinc White, and varying levels of tan to brown tinting. Sorry about the contrast, this is the best picture I have.
http://www.selectedplants.com/miscan/Blueeggs.jpg
First, define egg colors
White - common in games and others
Zinc White - bright white eggs, common in Leghorns
Tan - common in Wyandottes and other nominally brown egg laying breeds
Brown - Any of the Rocks or other brown egg laying breeds
Dark Brown - Marans and others selected for intense brown porphyrin coating
Blue - OOcyanin gene on chromosome 1 combined with genes for white eggs
Sky Blue - Oocyanin on chromosome 1 combined with Zinc White
Tinted Blue - cross of a brown layer and a Sky Blue layer gives light tan over blue
Green - cross between a brown egg layer and a white egg layer will produce this
Olive Green - cross a blue layer and a dark brown layer may produce this.
Porphryin (brown coating) production is a biopath, not a gene. There are at least 13 documented genes involved in porphyrin production. All chickens have the porphyrin biopath. Some chickens have one or more genes in the porphyrin biopath disabled which results in eggs that have no brown coating. In other words, a Leghorn has the genes to produce porphryin, but because one or more genes are disabled, a Leghorn produces white eggs. Some of the porphryin genes are sex linked, but to my knowledge this has not been documented in a peer reviewed paper. In some crosses, there will be a difference determined by which parent is male and which female. For most very dark egg layers, parent sex does not appear to matter.
Zinc White has the effect of almost entirely negating production of porphyrin in any cross where it is present. I am not certain if Cream Legbars carry the zinc white gene, but if they do, even crossing to a very dark brown egg laying line of Marans will wind up with less tint on the eggs.
Would a picture help? These eggs are from a cross of Silver Laced Wyandottes with blue egg laying Brown Leghorns. They have Oocyanin for blue, Zinc White, and varying levels of tan to brown tinting. Sorry about the contrast, this is the best picture I have.
http://www.selectedplants.com/miscan/Blueeggs.jpg
