I have three brown-egg layers and one blue-egg layer. For five days I got two blue and two brown eggs each day... Now I'm back to three eggs per day, two brown and one blue. Each time there was one little one, more blue/green in color, and one larger one, more bluish tan in color. But I know the two eggs had to come from the blue-egg layer since the other three have the standard pinkish brown eggs of brown-egg layers. Besides, yesterday I got a single egg and it was two thirds bluish tan with a blue/green end!
My duck just started laying and it's a white egg - and right now it's smaller than the chicken eggs!