Idioms: 'out of the blue' or 'out of the blues'?

[Mkayenglish]

Hello there everybody,
Is is 'out of the blue' or 'out of the blues' ?
I hope someone could help me!
Thank you.

[Michauek]

I think that it would be definitely "out of blue" or so does my dict PWN explains this idiom. e.g. to say sth out of the blue.

:)
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Experience is the name everyone gives to their mistakes. Oscar Wilde
Michal. I'm an english student :-)