What cause of cough mucus blood from mouth ?

Cold: There are sources of blood, like the stomach, the lungs and the nose and posterior pharynx. In time of cold or upper respiratory infection, there is mucous which is thicker than the plasma. This draws the fluid from the blood vessels in the nose and the pharynx which are to the surface and they can pop and hence you cough up blood. If possible other causes, please go see your doctor.