This fire in Colorado was burning in the area of the former Rocky Flats Nuclear Weapons Manufacturing Facility. This area is now a "wildlife refuge" but in realty is a nuclear superfund site that has radioactive ground contamination going back to the 1950's. Ground and water contamination has been absorbed by the flora growing in this high desert prairie and all of the grasses burning in this are are likely tinted with low levels of radioactivity. There was essentially a nuclear dirty bomb burning in Colorado's largest city... https://www.britannica.com/place/Rocky-Flats https://cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0800360