Sputum that is red in color, but not blood, can be seen in respiratory diseases as well as other systemic diseases. Common respiratory diseases are mainly manifested as different degrees of inflammatory reaction of the airway, such as lobar pneumonia will appear to cough rust-colored sputum, which can be red and dark, mainly caused by Streptococcus pneumoniae infection, a common bacterial pneumonia. It can also be seen in cardiovascular diseases, such as left heart failure due to various reasons, resulting in constant leakage of fluid from the lungs and dilation of capillary blood vessels, and coughing up pink foamy sputum, which can be clearly differentiated from other diseases by taking X-rays of both lungs as well as by testing cardiopulmonary and cardiac function and cardiac enzyme profiles.