Coturnix can lay any number of eggs
blue eggs in coturnix with no spots are eggs that were layed early by a hen with a blue "paint can"
That egg if she were to allow it to sit in her vent longer would have probably been a light tan or blue with speckles
When they have no spots what happens is the hen did not keep them in her vent long enough. wether it was stress that caused her to lay early or what the egg wasnt suposed to come out yet. taht's why it's not always common to get solid blue, solid white, or solid green eggs but tehy do happen and normally the shell is dull in color (not shiney because it didnt stay in long enough to get the bloom on it) and also is thin shelled in most cases. they CAN still hatch though but if they are really thin the possibilty they hatch is really minimal.
Normally tuxedo and range coturnix have the blue paint can as i call it
Buttons also lay blue and other oclor eggs when tehy do it's also because of stress or just laying early for some reason
Rule of thumb, the darker the egg the shinier the egg, the spottier the egg, the longer it stayed in the hen. the less spots, duller, and thinner the egg, the less amount of time it stayed in the hen.
