As a young guy, I must ask the question...especially being far less of a D&RGW and Colorado specific guy than many on here...
Are distinctions such as "classification lights" and "marker lights" not railroad specific? As I understood it, they served somewhat of the same roll...it is just as important to know from the caboose whether it is an extra (or has a second section) as it is at the locomotive. Just as the flagman would put white flags up on the locomotive and the caboose, the lights would be lit in a similar manner. Therefore, I'm failing to see as much of the distinction between the two.
I seem to have heard plenty of eastern railroaders refer to them as marker lights whether head end or at the rear. I prefer to keep the railroad specific terminology where possible...so they'll be "classification lights" for me from here on when dealing with D&RGW stuff.
Michael