During my recent trip to Colorado Springs, my brother and I set off on an extended road trip.
I don't know if the plant I'm trying to recall grows only at a certain elevation or a certain type of environment, but I remember seeing vast reddish plains covered with bushes of some sort, which were studded with beautiful yellow blooms. I never got out to examine one of these plants, but I can tell you some of the places we passed through.
I know we headed south and went through (not necessarily in this order) Pueblo, Cripple Creek, Estes, Manitou Springs, Canon City, and we stopped at the Royal Gorge. I'm sure my brother took a number of back roads, but this was the general area we covered.
Could the plant I'm thinking of be the Gray Rabbitbush (Chrysothamnus nauseosus)? It was stunning, but I couldn't seem to find it a few days later in the Colorado Springs area.