Being left home alone without supervision could be a sign of child endangerment on the part of your ex-spouse. The state of Colorado does not have a specific age limit regarding when children can legally care for themselves, according to the Colorado Department of Human Services. Ultimately, the parent caring for the child must ensure his or her well-being until the child reaches legal adulthood. If the parent chooses to leave the child at home alone, and something happens to place the child in danger, the parent is responsible.