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I am sorry to hear about this situation.
1) The ticket does not have to be sent by certified mail - it is still valid even if sent by regular mail.
2) You can contest it, or pay it. However, if you do not contest it, you do have to pay even if you live in another county or state. This is because the states recognize each other's court decisions and judgments.
3) If you do not pay for it, then best case scenario is that it would be put into collections. Worst case scenario is that a warrant would be issued for your arrest for not dealing with this ticket in time. In addition, your license may be suspended in CO, and if so, also in AZ, since both are members of the Driver License Compact.
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