What does "all blue skies" mean?

[Milon]

English Language Tests, Intermediate level

ESL/EFL Test #282 "English Slang Idioms (4)", question 4

The hard part of the transition was over. It would be all blue ......... from here.

(a) moon
(b) lagoons
(c) grasses
(d) skies

English Language Tests, Intermediate level

ESL/EFL Test #282 "English Slang Idioms (4)", answer 4

The hard part of the transition was over. It would be all blue skies from here.

Correct answer: (d) skies

Your answer was: correct
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what does all blue skies mean?

Milon

[Mister Micawber]

No problems; easy going.
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Native English teacher at Mister Micawber's