The Cleveland Clinic provides an online chart that breaks down the meaning of mucous color in relation to health and wellness. Mucous color can range from clear to black, depending on an individual's specific health conditions.
Healthy mucous is clear, according to the Cleveland Clinic. White mucous is a sign of congestion, which can be an early indicator of a cold or an infection, while yellow mucous is an indicator that a cold or infection has worsened. Green mucous is an indicator of an advanced infection, and the presence of green mucous combined with sickness lasting 12 or more days is a cause for concern.