First, which season? Second, Colorado is a pretty big state,so where are you interested in staying?
If summer, most Texans I have seen staying all season congregate in the Creede-Lake City part of the San Juans. Every RV park in that area seems to offer a monthly rate, although a few may have a longer rate.
If you are more interested in Colorado Springs or Estes Park, you may have a lot more difficulty finding one. Most of the private parks near me either have long-term RVs, meaning "permanent" and are not ones you would want to be in that long, or they primarily serve daily to weekly RVers and don't want long-term because they make more money during the busy summer season that way. For more info, see http://campcolorado.com/about-us/ (the Colorado Campground and Lodging Owners Association).
"Retirement is the best job I ever had!"
2015 RAM 2500 4x4 crewcab 6.7L CTD; 2016 Rockwood Signature UltraLite 5th wheel