Pepper Spray

[FoxtArt]

TLDR:
#1: The use of non-lethal is subject to the same standards as would physical force; e.g. if you would get arrested/cited for punching someone, you'll also get arrested/cited for any non-lethal use of force (pepper spray, taser, etc.)
#2: Colorado permits the use of the minimum level of reasonable force necessary to sustain a citizens arrest if you have witnessed the commission of a crime. That can include physical force, but again, it has to be the minimum level of reasonable force necessary. While unlike some/many/most states, Colorado doesn't explicitly limit that to a felony, I'd still only apply citizens arrest to likely felonies as a personal rule. Note this is the same law which security/retail/etc. detains people. Note that (potentially) lethal force is not permitted to maintain an detainment in any circumstance, you could only use lethal force while detaining if they are actively trying to kill you. This is not the law by which LEO uses to arrest people, security/retail/etc. cannot make use of LEO laws.

Kid's suggestion is also quite wise.

Disclaimer: Of course nothing you read on a public forum is legal advice.

Also for the love of all that's holy, don't deploy pepper spray inside your building. Face even a light a breeze and spray a little bit to get an idea why.