Fun fact - pea comb is linked to the blue egg gene in these breeds: Americana, Araucauna (sp?), and mixed breeds from them (prairie bluebell egger, many easter eggers). However, pea comb can be linked to straight comb in some breeds, including cream crested legbar (CCL), and there may be others I don't recall.
For Brahma, pea comb is linked to brown egg genes. So if you get brahma genetics mixed in with blue linked pea comb EEs, there's no telling by looks what genes your birds will have.
Comb type is on the same gene as egg color is I think how it works, and pea comb is dominant, while straight comb is recessive.
Many EEs are based on araucana or americana lineage, so pea comb means they have the blue egg gene, and will therefore lay green or olive, or maybe blue if they're bred for it. But not always. Straight comb EEs are also a thing (CCL based), and straight comb OEs with head poofs are so cute!