All the offspring from this specific mating will have a darker coat color phenotype, regardless of whether they have the FF or Ff genotype.
Prediction of the outcome of their offspring
When two heterozygous horses are mated (Ff x ff), where both parents are darker colored, the offspring's phenotypic outcomes can be predicted based on the principles of Mendelian genetics.
In this case, the Ff parent is heterozygous for the coat color gene, where F represents the dominant allele for the darker color, and f represents the recessive allele for a lighter color. The ff parent is homozygous recessive, having two copies of the recessive allele.
The possible genotypes and corresponding phenotypes of the offspring can be determined using a Punnett square:
Both genotypes include at least one dominant allele (F), which results in a darker coat color.
Therefore, all the offspring from this specific mating will have a darker coat color phenotype, regardless of whether they have the FF or Ff genotype.