Sadly, forums seem to be on the severe decline and ones for Colorado are in short supply. This site (http://www.coloradofisherman.com/) seems to be okay, but is not 100% fly fishing focused though it is active enough for a narrowly focused site. My guess would be someone there can answer your question. My personal recommendation would be to check with your local (or nearby) shops. I would say talk to shops in Colorado Springs or Denver (my recommendation for Denver area would be Charlie's Fly Box in Arvada), and see what they recommend for Colorado brook trout.