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your first plan(ameraucana x barred rock/Leghorn) would have not worked as plan as the Blue egg shell on the Ameraucana is linked to its Pea comb, making any Rosecombed looking legbar a white egg shell layer instead, and only the Walnutt combed birds would have laid blue eggs... this is less tricky with your current project, but still tricky none the less... the Rosecomb Leghonr comb genotype is R/R p+/p+ and o+/o+ the Cream Legbar comb genotype is r+/r+ p+/p+ and O/O now the O gene is linked to the p+ gene by 4 MapUnits, this means that wherever the p+ gene goes there is 96% chance the O gene is going to be there too.. now a cross of such genomes would produce the following genome, R/r+ p+/p+ and O/o+ this bird would have laid light blue eggs, now what did you do after the F1? did you cross it back to Cream Legbars? or back to Rosecomb Leghorns?.. why are still getting Inconsistence blue egg color shade? well thats because of the O-p+ linkage, seems like most of your birds are still heterozygotes for the O/o+ gene, But it seems like you do have a keeper on one of your pullets, she seems to be O/O and therefore p+/p+ having two copies of the Cream Legbar single comb gene, while also having the RoseComb gene, I would take this female(and cull the other pale blue egg shell birds) and mate her back to Cream legbar and go from there