Was just in Paonia over the weekend, and came out of town via Grand Avenue to CO-133. Looks like all 5 or 6 signs that marked the entire 0.7 mile length of CO-187 have been removed.
Has CO-187 been decommissioned as of late? I know it's one of the shortest state highways in Colorado, so I don't know how recent this has happened, or if CO-187 was one of several routes that CDOT has decommissioned as part of a larger highway reorganization project.
http://www.coloradodot.info/about/transportation-commission/approved-resolutions/resolutions-january-2010-december-2010/december-2010-resolutions/1932-highway-187-to-delta-county.pdf
Matt Salek has a great site for questions like that. Here's his entry for SH-187:
http://mesalek.com/colo/r180-199.html#187