Assuming CO stands for Colorado, there are rules but tire chains are just one option. All weather tires are winter rated and should have a mountain/snowflake on the side wall. Are you sure you need to buy chains? According to this link, M+S or winter tires will suffice. If you're in the code 16, well you probably shouldn't be out there anyways.
I don't live in this area, but just went through the same thing. One of my kids was concerned cause her friend told her she must have chains in her vehicle on specific roads and special times of the year. After reading the regs, it turned out to be a different story.