The world is changing. Today people can sit in the comfort of their own homes and earn advanced degrees via online classes. This naturally has led many instructors to offer online concealed carry classes.
The Colorado State Statutes do not directly restrict students from qualifying by taking a digital or online class. Many states have have started to revise their laws to clarify how they feel about online instruction but Colorado, so far, has not.
HOWEVER, each county sheriff does have a certain level of discretion in accepting training certificates and, as you may have guesses, most counties will not accept a training certificate that was generated from an online class. When I first started teaching classes in Colorado, I received many phone calls from counties who wanted to ask me questions about my class format. My students have also been asked for details during the application process.
If you find the opportunity to take an online Colorado CCW class I suggest you pass. In addition to a poor educational experience, you will also find that your money will be wasted when your certificate is rejected by your county sheriff.