I haven't seen another supposed source for the blue egg shell breed used in the cross. What other breed was suggested? My understanding is south american breed ancestors and European/North American breeds which are derived from them share the same locus for the blue egg gene. With that - they all
should behave the same way in terms of being linked to the pea comb. The two traits can and are often separated as demonstrated by pea combed Easter Eggers laying brown or white eggs, and straight combed chickens like the Cream Legbars laying blue eggs.
There are two other breeds which are isolated to China that also carry blue egg genes which according to this:
http://saturn.adarc.org/paleo/site/html/posts/2013-09-10-Oocyan-EAV-HP.html
evolved the blue egg shell gene at a different location via the same ERV. With that, in theory you might be able to get a more vibrant blue if you have the ability to find someone selling said asian breeds which I do not know of anyone state side or otherwise that does.