Daylight during an early spring snowstorm is ending amid the “blue hour” just before nightfall at Union Pacific’s North Yard fuel tracks at Denver, Colorado, on April 15, 2013. The former Rio Grande facility features an all-EMD lineup of GP38-2 No. 506, SD70M No. 4333 and SD70ACe No. 8688, with some ever present GE products lurking behind.