Does Colorado have non-exclusive buyer agency agreement?Many Thanks

As far as the agency part of your question is concerned, the short answer is "no," because in Colorado, a broker cannot be an agent without a written contract establishing that relationship with the buyer.  However, many real estate brokers are willing to work with a buyer without a written agreement that makes the broker exclusive.  If an agent assists a buyer without a written contract, the default relationship is that of transaction broker (versus agent) and there is no agreement or contractual obligation for the buyer to use that broker exclusively, although most buyers end up doing so if they are happy with the broker. The difference between an agent and transaction broker is another issue, beyond the scope of this answer.

Even if a buyer and broker agree to enter into a written contract, all contracts are negotiable and do not have to be exclusive.  Rather than an exclusive-right-to-buy contract, the parties could limit the contract to a specific property or exclude certain sellers.  Even particular areas, subdivisions, and types of properties could be excluded.

If you have any concerns or questions about an exclusive agency (or transaction brokerage) contract, you need to discuss those with the broker and make sure your questions and concerns are addressed and then determine if the two of you can negotiate a contract that is mutually acceptable before you sign anything.