Usage of colon versus ellipsis when restating a definition
Solution 1:
It comes down to style. The written word is merely an attempt to codify the spoken word.
In this case, they both convey a subtle difference in intent.
The ellipsis is a pause and wait for effect. The colon is a warning to the reader that the next idea is the response.
Both are acceptable.
The ellipsis is meant to convey a bit of drama. If it were an episode of CSI, the music would pump up at that moment and they'd give the answer.
If it's just a statement of thought process, go with the colon.
The detective couldn't help but feel uneasy being shown in by his lead suspect. But, the suspicion against the butler was just that: a suspicion.
The better question is colon vs semicolon vs comma here.
Again, I'd argue, style is style.