where did the phrase out of the blue come from
Out of the blue (idiom) "Out of the blue" is an informal English language idiom that describes an event that occurs unexpectedly, without any warning or preparation.[1] It is used as an adverb. The "blue" in the phrase refers to the sky, one from which a sudden thunderstorm is unexpected.[2]
Robin egg blue Robin egg blue, also called eggshell blue, is a shade of cyan (greenish-blue color), approximating the shade of the eggs laid by the American robin.