The pea comb gene and the blue egg gene are closely located to each other, and are usually inherited together, whichever alleles of each are present in a parent bird.
Let's assume that an EE hen is het for blue egg and for pea comb. That genotype is Oo Pp. She has one blue-egg gene and one not-blue-egg gene, and one pea-comb gene and one not-pea-comb gene.
If the two genes were not closely linked, there would be equal probabilities of her contributing any of the following gene to her progeny:
O P (blue & pea)
O p (blue & not-pea)
o P (not-blue, pea)
o p (not-blue, not-pea)
With linked genes, the more closely located they are on the chromosome, the more closely linked they are. It is still possible for the genes to be inherited separately, but the probability is less. Someone else has done the math based upon the distance these genes are apart and there is a 3% chance than they will be inherited separately. When that occurs, it is called crossover, and getting it to cross back is equally unlikely.
Find and read any poultry genetics book or website and you will find this information.