[SeekAndFind]

What of they vote to secede but the State of Colorado won’t let them? Then what?

[Texas Fossil]

Is it for the Legislature to decide?

Or a state referendum?

I doubt it will happen, but if it did, WOW the possibilities.

[Ghost of SVR4]

What of they vote to secede but the State of Colorado won’t let them? Then what?Then the Sheriff (highest office in "the land") needs to round up a lot of men with guns and kick Federal and State agencies out of that county. That county needs to use its own currency and they can run a currency exchange to trade with the "outside" world (so the state cannot tax them).

[Blood of Tyrants]

Then they sue. West Virginia seceded from Virginia without permission from Virginia. Congress gout around it by claiming that WV got permission from the “recognized” Virginia legislature (essentially a bunch of self appointed people who claimed to represent all of Virginia).

[Lurking Libertarian]

What of they vote to secede but the State of Colorado won’t let them? Then what?

Then nothing will happen. Under the U.S. Constitution, a state cannot be split into two without the consent of both the state Legislature and the U.S. Congress. Constitution, Article IV, section 3, clause 1.