He has committed the act of bigamy in CO. You can report it to law enforcement and the local DA. However, it is doubtful that they will want to get involved and I do not know one single occasion in 21 years of practice in which someone has been charged with bigamy.
Your better option is to file for a divorce. CO is a no fault state. So, his marriage to the other woman will have very limited value. However, you obviously do not want to be with him anymore and should simply make it official.
The information provided in this answer does not create an attorney-client relationship. If you are interested in his legal services, feel free to call Chris at (303) 409-7635 at his law office in the Denver Tech Center. All initial consultations are free of charge.
Since you were never divorced, there will be issues regarding assets that you and he have accumulated since your marriage. Either of you may have retirement funds, a house, savings, etc. It would be best to consult a family law attorney. Mr. Leroi is correct- if you don't want to be married, you need to file for divorce. His "marriage" to his current wife is not legal.
I assume that you have been physically separated for some time. This can create a lot of risk as, despite the way some people act, marriages do not simply expire when you are separated long enough. The mess your husband finds himself in is only one of many. He is guilty of a felony if a prosecutor is willing to pursue it and his current marriage is invalid. Additionaly, any debts or assets you acquire are subject to being split with the other spouse and if either of you becomes disabled the other may end up paying spousal support despite years of separation.
The best thing you can do is to file for divorce. It sounds like it is past time for the marrage to be over.
You can reach Harkess & Salter LLC at (303) 531-5380 or info@Harkess-Salter.com. Stephen Harkess is an attorney licensed in the state and federal courts of Colorado. This answer is for general information only and does not create an attorney client relationship between Stephen Harkess or Harkess & Salter LLC and any person. You should schedule a consultation with an attorney to discuss the specifics of your legal issues.
I agree with the answers already provided. In addition, at this moment, if you want to do nothing, you may choose to do nothing. The benefit may be that if your husband dies while you are still the spouse, and there are any benefits to go to the spouse, then you would get them and the new wife would not. HOWEVER, there is a big risk too!! If your husband incurs debt, especially medical debt, then you may be held to be jointly responsible for that debt. You could end up paying attorney fees for a man from whom you've been separated for many years.
I suggest you look into filing for divorce. It appears that he would want to be divorced as well, so if he will sign all of the papers with you, it can be a pretty quick (just over 3 months) and easy process. You don't state whether you have any children with this man, but if so, support issues would need to be discussed.
This legal information is provided for general legal purposes and does not establish a client-attorney relationship. Because of the limited information provided in the question, it is difficult to be certain that Counsel is answering the question correctly. You are encouraged to seek further information from an attorney directly so that follow up questions may be asked if necessary.