Marital property is that which was acquired during the marriage. A Colorado Court must divide all martial property in a divorce or legal separation. CRS 14-10-113.
However, it does not have the jurisdiction (power over) to divide separate property. That applies to both premarital separate property and post-Decree separate property.
Based on statute, Colorado Court of Appeals, and Colorado Supreme Court cases, all post-Decree property is separate property. Marriage of Coplin. Hiner. Campbell. Price.
However, you must designate and claim premarital separate property in order to protect it.