Q. Is the revenue earned from CO required to be reported in CA as nonresident?
A. Yes, but nobody does. See: http://money.cnn.com/2013/06/28/pf/taxes/business-traveler-tax-threat/
I assume from your description that you are physically performing the work, for the Colorado client, in California, while you are there as a student. That makes it, technically, CA source income.
You also report it on your CO resident return and CO gives you a credit for the tax paid to CA. So, there will be little or no double taxation, but you have the cost and hassle of filing two state returns. Do the nonresident state return first.
