Since most municipalities in CO didn't buy into the first attempt at common sense in 2018 (SB 18-144), they now don't have to opt in.
www.bicycleretailer.com
Since Colorado is a Home Rule State, municipalities can opt out. I've already read where the mayor of Fort Collins is not happy with this law and may wish to opt out of it. The article also said the mayor in question claims to be an avid cyclist. My guess is that they one of those kitted out roadies with $10K of bike, wearing at least another $1K of gear and no idea that there is a Cycling World that goes well beyond their obviously limited viewpoint of it all.

Colorado Safety Stop signed into law by Gov. Jared Polis
Colorado Safety Stop signed into law by Governor Jared PolisBicyclists, users of low-speed conveyances, now have new safe and legal option for navigating intersections statewideDENVER — Bicyclists in Colorado now have a safe and legal option for navigating through intersections after Governor...

Since Colorado is a Home Rule State, municipalities can opt out. I've already read where the mayor of Fort Collins is not happy with this law and may wish to opt out of it. The article also said the mayor in question claims to be an avid cyclist. My guess is that they one of those kitted out roadies with $10K of bike, wearing at least another $1K of gear and no idea that there is a Cycling World that goes well beyond their obviously limited viewpoint of it all.