Because you are a resident of Nebraska, you are required to file an income tax return in Nebraska if you had any income (no matter where earned) and were required to file a federal tax return. Here is information from the Nebraska Department of Revenue on a similar FAQ:
I'm a full-year Nebraska resident, but my income is from another state. Do I have to file a Nebraska Individual Income Tax Return?Yes. You must file a Form 1040N.
For regular income, you will receive credit for any taxes paid to the other state by completing a Nebraska Schedule IIand attaching a copy of the other state's income tax return. Nebraska income tax is imposed on all income which is earned while a resident of this state.
You may reduce your federal adjusted gross income on the Nebraska Schedule I for pass-through income received from an S corporation or LLC in a state other than Nebraska.
http://www.revenue.nebraska.gov/question/indiv_quest.html#iquest09
Note: Be sure to do your
non-resident Colorado return first so that any taxes paid to Colorado can be reflected on your Nebraska return.
Here is more information on filing a non-resident return in TurboTax:
https://ttlc.intuit.com/replies/3302052
