State tax filing

Basically, yes that still applies.  NC charges a flat tax rate on NC-derived income.  NC's is 5.25%.  CO has switched from a flat 4.63% tax rate to one that gradually increases starting at income level $150,000 up to 6%.  You would prepare the NC return first and then claim a credit on your CO return against the NC tax.  You would probably not get a full dollar-for-dollar tax credit as the credit is capped against what you would owe CO on that same income.