Hmm.. Found this on Medical Mythbusters
Here's the link: http://shs.osu.edu/blog/medical-mythbusters-green-snot

True or False: My snot is green so I need an antibiotic, right?

A:* False!!

This is one of the most tenacious, and frustrating, medical myths out there: that clear snot indicates a viral infection that will clear on its own while green snot automatically means a bacterial infection that requires an antibiotic for treatment.*