Color is also polygenic. The offspring inherit half their genes from each parent. Some of these genes are more dominant than each other.
The only color of Cochin that crossed with a dark Brahma would have “dark” or rather silver pencilled offspring, would be silver pencilled.
With all other colors the offspring would be a color that is an intermediate between the parents colors.
Dark Brahmas (genetically silver pencilled) have these genes: partridge, pattern gene, and silver.
Partridge is recessive, pattern gene is dominant, and silver is sexlinked dominant. But it is not so simple. Partridge may be recessive but in the heterozygous state it still expresses to some degree. Pattern gene may be dominant but in its heterozygous state the pattern is incomplete. In the heterozygous state of silver, you get a yellowish color.
