If NC was incorrectly withholding taxes for your time as a CO resident, you could file amended NC returns for a couple of those years too. NC gives you three years from the due date of the original return to file an amended return. https://www.ncdor.gov/taxes-forms/individual-income-tax/when-where-and-how-file-your-amended-individ...
Be aware that if you file amended NC returns and receive a refund of the incorrectly withheld NC taxes, and if you previously deducted those taxes on your federal return, the refund would be taxable at the federal level.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
