That's exactly what I was wondering. If you crossed one of these Chinese blue-egg breeds with an Auracana, Ameraucana or Cream Legbar would you get a brighter, deeper blue egg? I'd like to see what would happen!
I found this in a study published in Nature here:
https://www.nature.com/articles/srep26484
Candidate retroviral insertions specific to GA chickens
The genetic determination of blue egg shell coloration has been identified in Araucana chickens; it has been revealed that EAV-HP insertion promotes the expression of
SLCO1B3 gene in the uterus of the oviduct in Araucana chickens, which causes blue egg shell formation
9,
29. Our results identified retroviral insertions from three GA genomes in
SLCO1B3 gene equally. Dong Xiang (DX) chickens are another blue-egg laying breed
29; EAV-HP insertion was also identified in the DX genome sequence adjacent to the insertion of the
SLCO1B3 gene in GA, which indicates that GA and DX share genetic characteristics with other breeds that lay blue eggs. All of these results are consistent with previous reports
9,
29.
As we detected the presence of TE insertions using multiple TE probe sequences at the breakpoint, it was necessary to verify that the sequences of TE insertions are identical. In order to validate the presence of EAV-HP sequence, we carried out local de novo assembly with Velvet
30 using the reads mapped within 1000 upstream and downstream of the candidate breakpoint. From this process, we obtained several contigs and aligned these with the TE probes we used for TE identification. Next, we conducted multiple sequence alignment over sequences recovered from the above process of several individuals, and retrieved partial conserved TE sequences (142 bp) from 3 GA and DX genomes. Collectively, the commonly identified insertion of EAV-HP in three GA chickens was identical to that of previous experimental studies
9,
29.
So...sounds like same gene slightly different location on DNA strand?