There is no age set by statutes in CO regarding the child having a choice. In fact, you can check with any family lawyer in CO, the childs wishes are only considered when you use a CFI, and the children's opinion is rarely taken into account.
If the mother is a fit and competent parent, and has no direct proof of physical abuse, then he doesn't have a chance, only if agreed upon by the Mother. Once the primary custodian is set, the courts rarely change the primary parent unless there is an agreed upon change, or if the non-custodial parent can prove change in circumstances which is a very difficult burden for the non-custodial parent.
the child physically cannot leave the custodial parent's home until he/she reaches the age of 18.
If the mother is a fit and competent parent, and has no direct proof of physical abuse, then he doesn't have a chance, only if agreed upon by the Mother. Once the primary custodian is set, the courts rarely change the primary parent unless there is an agreed upon change, or if the non-custodial parent can prove change in circumstances which is a very difficult burden for the non-custodial parent.
the child physically cannot leave the custodial parent's home until he/she reaches the age of 18.