Greetings @Little homestead from up north of Denver on the front range. Welcome to BYH!
The guide that Bay linked is excellent for information and guidance. I'm not familiar with your soils there, or how large an area you're trying to develop, so can't really help much... If you have a farm & garden center nearby or sometime animal feed stores have folks to help, you could ask them what local farmers use for pasture seeding. I know our Ace hardware in Brighton is attached to Agfinity and they carry all kinds of seed mixes for whatever you're trying to accomplish. You might consider contacting your county extension agent for assistance. He/she can most likely provide assistance or direct you to the right folks to help you. You can contact the source of the link document as well at Colorado State university and see if they can help.
This may not be for you but we had the Co-op come out and take soil samples for analysis at Uneversity of Tennessee. There was no charge since we had them come out with several tons of lime and fertilizer. Even over winter our cool weather grasses grew like crazy.