The first step is to look at your contract with the venue. Most contracts include something called a 'force majeure' clause which allocates the risk of loss if performance is hindered, delayed, or prevented because of an event that the parties could not have anticipated or controlled. If the clause applies, it will often relieve the parties from performance of their contractual obligations. In your case, that would be your contractual obligation to have your wedding at the venue. See Gillespie v. Simpson, 588 P.2d 890, 578-79 (Colo. App. 1978) (suspending the duties owed by one party of the contract), Smith v. Long, 578 P.2d 232, 234 (Colo. App. 1978) (completely relieving a party's duty to perform).
Once you establish that your contract has a force majeure clause, you must then determine if COVID pandemic is covered under the provision. This would take into account the timing of the wedding as well as government regulations in place at the time of the breach, and the specific language of the clause. Many force majeure clauses have a catch-all that would likely apply.
Colorado does not imply 'best efforts' in the clause, so if the force majeure clause applies, you have a reasonable avenue for relief of getting your deposit back even though "others" are having their wedding anyway. As for the venue's claim that COVID is not their fault, that is exactly the point of a force majeure clause - to cover unforeseen events that are not the parties fault.
Finally, even if you do not have a force majeure clause in the contract, other contractual claims such as frustration of purpose or changed circumstances may apply to give you relief. If you would like to discuss the matter in detail, please contact us at https://www.robinsonandhenry.com/locations/ to start a free case assessment.