About running nose

Colorless - Your healthy is perfect and you can breathe comfortably.
Wet and Colorless - You have allergic disease or irritate something around yourself.
White and Thick - If you are smoker or second hand smoker that means your sinus
getting dry.
Yellow or Green - you are infectious in sinus or have cold.
Brown or Black - Just not bacteria in your sinus, it is moldy.
Bleeding - You blow it seriously or pick it until destroying capillary of sinus.