I think my cold is turning into a sinus infection. day 6 of cold. mucus turning from clear to diff colors, like yellow. my ribs are sore from coughing?

Could be: It certainly could be. The average cold lasts 7 - 10 days. Typically with a sinus infection you start to feel more ill, run a fever, sinus pressure, thinking nasal discharge, & worsening cough.

Day 6 of URI: Although it seems like it has gone on forever by now, day 6 of an upper respiratory infection is only about halfway through the normal course. Color of mucus is not a reliable indicator of bacterial infection. A fever (temp >=101.5) or symptoms that are worsening after 2 weeks are more important. But if you are holding in your cough due to rib pain, that may delay healing, so see a doctor.