I also have a C920: it's fairly infamous for the "Smurf effect", where it tends to make everything look unnaturally blue. Setting the "white_balance_temperature" setting manually improves this situation substantially! Depending on your OS, you might have to first set a "white_balance_temperature_auto" to "off" and then set a "white_balance_temperature" in Kelvin. [In OpenBSD, we recently added this ability, but conflated the two controls into one. YMMV will vary by OS!]