When I bought Coturnix hatching eggs last summer, most were definitely rust/brown toned, but a few were either green or blue toned. Very pretty. Why, I don't know -- breed/genetics, diet, age?
Haven't got an all solid color egg but I did get a bluish/greenish egg once that looked like it go fried coming out of the quails tushi LOL I sill have it to@ Blew it out so I could keep it.
That's really neat. I thought they were all white with brown speckles. Didnt know you could occasionally get something else. It'll be something to look for if I can hatch the eggs I'm getting. Gathering eggs will be like a treasure hunt. lol
You really never know. Might find an odd color one or a double yolker which I have a couple of those as well. I'll take a picture or two of the odd eggs I've gotten and post them on here later.