I think this is the leaf katydid which is widely distributed in Colorado, found in both eastern and western Colorado and also common in many urban areas. They are related to crickets and grasshoppers. It is one of the most often heard Colorado insects, making clicking calls in trees and shrubs during late summer. They make the noise by rubbing a hind leg on one wing, similar to cícadas, and use it to attract the ladies. I knew they existed as I hear them quite often in the evening but seldom see them. Anyway, this one was on the sidewalk outside my door late Saturday afternoon. And, they were quiet. I almost stepped on it.
