As of May 2019, the traction laws in Colorado were changed. The new law applies differently during different types of snowstorms and on different roads in Colorado, but the safest bet is to make sure you have either AWD or snow tires (or both) anytime you’re driving in snowy conditions. Drivers who cause accidents or who block traffic and don’t have one or both of these (or one of the alternatives permitted by the new law) risk fines of $132 to $656 in addition to previous repercussions in both criminal and civil courts.

CDOT has a great summary of the different types of storms and areas this can affect: https://www.codot.gov/travel/winter-driving/tractionlaw. 

For a full look at the final bill that was signed, you can click here: https://leg.colorado.gov/sites/default/files/2019a_1207_signed.pdf.