Let me cite two examples, one using "—" (dash) and the other using ":" (colon):
John has three sisters — Sita, Mita and Rita.
John has three sisters: Sita, Mita and Rita.
Grammatically, both sentences are correct. The only issue here is the use of two different punctuation marks as one sentence uses "—" (dash) and the other ":" (colon).
Which punctuation mark is correct? What is scope of usage of each of the punctuation marks? Can they be used interchangeably in the given context?
I am not going into the issue of m-dash or n-dash; nor am I concerned how a "—" (dash), when occurring in a pair, is to be used.
Can anyone shed some light?