'Out of the blue' is a terse form of the expression 'out of a clear blue sky' (to mean 'unexpectedly, without foreshadowing').
It is not really a figure of speech, but an idiom. ('idiom':: an established expression in a language where the meaning is not necessarily what one would anticipate from the given meaning of the individual words).
its an idiom
Onomatopoeia
Onomatopoeia
Simile
I believe this is a simile.
its an idiom
idiom
simile
Onomatopoeia
Onomatopoeia
Simile
i need help
I believe this is a simile.
A figure of speech
Idiom
personification
SIMILE