Zigadenus venenosum Meadow Death Camas
or Zigadenus paniculatus Foothills Death Camas
According to the USDA plant list and other resources Z. Venenosum is not in Colorado but is in NE Utah and Z paniculatum is found rarely in Moffat and Rio Blanco Counties. In Z. venenosum the tepals are narrowed to very short claws. Z. paniculatus the lower flowers may be staminate and the upper ones perfect. I cannot be sure which this is from the photo though I suspect venenosum.