Hank,
Thanx for the update. There is a nice photo of 456 in the Mudhens book in 1936 in Gunnison with the backup light. Page 73. Also on Page 80 is 456 in Montrose in 1951 still with the light. The NG pictorial Vol XI on page 85 shows 454 with a light in 1950. So I don't think the lights or tenders were switched between 454 and 456. Perhaps 454 got a tender or light from another unit?
I'd still like to know when 454 got it's light just for history's sake. I have a PSC/MMI On3 454 and will be adding the light since I model the D&RGW from the late 1930's through the 1950's.