The reason you did not find a law that makes OC legal is because that is not what laws do. Laws make things unlawful. Sometimes you will see something in the law that looks like it makes something legal but it is really just an exception for something that is not.
You will not find a law that says it is legal to eat popcorn without using your hands unless there was first a law that said eating popcorn was illegal in the first place and eating it without using your hands was an exception to the prohibition. The law did not make eating popcorn without using your hands, it only provided an exception to the eating of the popcorn.
There are no laws against OC generally (with minor exceptions) in Colorado. So, whatever is not illegal is by default legal.
Your link to the COS code is great and it defines where is it not legal to OC (although CC is perfectly fine with a concealed permit where no metal detectors are in place.)