So I took a quick jaunt down to the Front Range last weekend (which was a horrible mistake, but that's not the point here) and drove by the west end of CO 263 in Greeley. I was going to clinch it, but there was some construction closures and it was only marked as "E 8th St" on the construction signs. There was still 263 signage on US 85, but I don't think there was any on the route itself, as far as one could tell driving by at 9:30 PM. Additionally, it doesn't show up on the CO data explorer:
https://dtdapps.coloradodot.info/otis/HighwayDataI feel like it's been decommissioned and I should axe it, but I want to see what other people think.