First, personal use of marijuana is not yet legal in Colorado. The vote must be certified, which take about 30 days from the date of the ballot measure.
Second, and to your question, the use of marijuana would be one factor the court may look at when determining whether the child is endangered. That is, essentially, what the court will be looking at in the context of what is in the best interest of the child.
I hope this helps.
Nothing in this communication should be considered legal advice. Nor should this communication lead you to believe that an attorney-client relationship has been created. Only after thorough analysis of your case with you in my office can I provide effective legal advice on your specific issue.