Yes - in order to file a California tax return using TurboTax you must purchase the California state module. It shouldn't be difficult to complete a California non-resident tax return - it's very common for taxpayers to have to file both a non-resident and a resident state tax return and TurboTax can handle that situation. The program's built-in questionnaire will basically walk you through.
In TT, be sure to complete your non-resident CA return before you do your home state CO return, so that CO credits you for the taxes paid to CA on that income. (Your CA capital gain is taxable by both states.)
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
