The celadon gene doesn't turn the egg blue. The eggs naturally have biliverdin (previously oocyan, the green pigment responsible for blue shell color in chickens and quail) in the shell, even as the wild type. It is coated in protoporphyrin (a red pigment that looks brown) in a base coat and heavier application of speckles. The celadon gene, in homozygous form, removes the protoporphyrin coating, revealing the actual shell color underneath. This can range from white to blue to green, depending on the amount of biliverdin. You can select for hens who lay eggs that have higher biliverdin content over time, but it's tedious because you can't tell the quality of the rooster for an extra generation (until his daughters lay).
The website linked above is just breeding normal eggers that they've selected for more biliverdin and less speckling, not actually celadon eggs. The 'speckled' celadon eggs are normal, wild-color eggs.
Look at the photo from that page; the whole photo has a green cast to it. Adjust that and you can see the problem with their claims...
The top 3 eggs are the cleanest of the group, no base coat muddying the color, but unfortunately the color lacks biliverdin. The eggs to either side of the bottom center egg are just normal eggs. The rest are all poorly-colored celadon eggs with light to heavy base coat leakage.
Good celadon eggs can be photographed in normal lighting without that green cast to the photo, and the eggs should be
blue, not green. Here are some of mine for comparison. Plain lighting, no weird green cast that photos get when people are trying to make their white or brown eggs look blue by adjusting the color of the photo.
Technically, to answer the original question, all quail eggs are already "olive" by virtue of being 'brown over blue' the way olive eggs are in chickens. There IS a white egg gene in coturnix, though it's very rare. When you cross a normal egger to a celadon egger, you just get normal eggers that are heterozygous for the celadon gene. They will lay a normal wild color egg.
here's a better site for looking at Celadon vs normal egg colors.
@Susan Skylark since you asked
