Martyn:
The D&RGW used a variety of switch stand targets or indicators over the years. The first were the stub switch "banjo" type markers. Later, after stub switches were gradually phased out, they used round targets. Sometimes lighted marker lamps were placed on top of the markers. Those were primarly used on the standard gauge main lines, but some were used on the narrow gauge. One of my prized possessions is a switch marker lamp from Alamosa. It was from the wye. The son of a D&RGW brakeman gave it to me years ago. In later years, the D&RGW replaced some of the round targets with other types that you can see on the C&TS.
The D&RGW had standards books for switch design including specifications for the various targets. These books changed over the years and the one I have is from the late 1890s and does not reflect the current standards seen on the D&S and C&TS or what is left of the D&RGW standard gauge.
I am working on an article for the Prospector magazine that will be published sometime when they are ready.