Out of state is not legal. In state is legal. If you:
1. Have lived in CO for 22 days
2. Have an address in the county where you wish to vote, which can be a hotel or homeless shelter, even if that address is only a few hours old. Also, you do not need to provide documentation of that address.
3. State you intend to relocate to the county
then, you may register and vote in the count all at once on election day. Even if you later change your mind and do not relocate, your vote is legal. The issue is that intent is impossible to prove.
More traditional systems involve proving an address 60 days or more before the election and still living there on election day.
22 days?