Un vent d'or is part of the sentence. It can't be removed so is not a proposition incise which would have been a use case for a tiret cadratin.
To mark a pause, points de suspensions (ellipsis) are commonly used:
puis… un vent d'or.
Yes before a colon, a (thin) space is always expected.
Note that before other two-stroke punctuation marks (semicolon, exclamation and question mark), when rendering the text on a system that doesn't make a difference between a thin space and a regular space (typically web pages), the norm differs between Québec and France.
The former one tells to use no ...