Phlegm or sputum is mucus, a sticky substance that comes from your respiratory tract. It often comes out when you cough or expectorate and it often indicates that you may have some form of respiratory tract disease. Sputum color (or sputum colour) usually helps doctors diagnose your condition, when evaluated in relation to your symptoms, your medical history and physical examination, as well as laboratory tests. Sputum cytology and sputum culture also help determine the causative agents associated with your sputum color.

Early morning sputum is the best specimen to examine since this provides the ideal amount and composition of your mucus. Otherwise, sputum samples taken later during the day may be tainted by coloring and other substance from food and drinks.

Different Sputum Colors and Their Meanings

Sputum from your respiratory system is often mixed with saliva produced in the mouth. It may contain microorganisms, cellular debris, immune cells, dust, and blood components. Sputum color may depend on the disease process and the quantity of the components mentioned. Therefore, your sputum may have a wide variety of colors and character, such as clear, white, yellow, gray, green, pink, red, brown, black or rust-colored.

1.       Clear/White/Gray Sputum

It is normal for you to cough out a small amount of clear sputum occasionally. However, excessive production of clear or white sputum may be abnormal in some cases, such as:

• Respiratory tract infection caused by a virus - clear to whitish sputum
• Asthma – thick, white/yellow sputum
• Chronic bronchitis (COPD) – clear/gray sputum
• Pulmonary edema (presence of fluid in lungs) – clear to white, frothy sputum
• Postnasal drip
• Allergic reaction
• Gastroesophageal Reflux Disease or GERD

Cigarette smoking and air pollution can result in the production of grayish phlegm. Clear or white phlegm can also precede the appearance of yellow or green sputum, especially during the early stage of an infection.However,white, frothy sputum may be a sign of health failure, leading to an increase in fluids in the lungs or pulmonary edema.

2.       Yellow Sputum

Yellow sputum colour is often seen in infection, chronic inflammation, and allergic conditions. It is due to the white blood cells called eosinphils, which are associated with allergic conditions causingairway hypersensitivity, or neutrophils, which are associated with infection. Examples of conditions when you may have yellow sputum include:

• Acute bronchitis
• Acute pneumonia
• Asthma

A light-yellow sputum color may be a sign of a normal immune system function, signifying that it is fighting a viral upper respiratory tract infection. However, thick, dark-yellow phlegm may indicate a bacterial infection, which may occur in your sinus or lower respiratory tract, such as chronic bronchitis or pneumonia. Seek medical attention immediately.

3.       Green Sputum

Green sputum color is an indication of long-standing or chronic infection. It results from the breakdown of the neutrophils, which causes the release of enzymes from the cells. Non-infectious, but inflammatory conditions may produce large amounts of greenish mucus, but infectious conditions are associated with green sputum that has a large amount of pus (more purulent). These conditions may include:

• Pneumonia
• Lung abscess
• Chronic bronchitis
• Cystic fibrosis
• Bronchiectasis

Aside from green sputum, you may also experience symptoms such as fever, cough, weakness, and loss of appetite. Consult your doctor immediately for proper evaluation and treatment.

4.       Brown/Black Sputum

Brown to black sputum color indicates the presence of ‘old blood.’ The color is due to red blood cell breakdown, resulting in the release of hemosiderin from your hemoglobin. Organic as well as non-organic materials may also cause the brown or black sputum colour. Examples of conditions where dark-colored sputum may appear include:

• Chronic bronchitis
• Chronic pneumonia
• Coal worker’s pneumoconiosis
• Tuberculosis
• Lung cancer
• Chronic smoking

If you are a chronic smoker, it is best to stop smoking. Consumption of dark-colored foods and drinks such as coffee, wine or chocolate may also give you brown or black sputum, especially if you have acid reflux. Consult your doctor for further evaluation and treatment.

5.       Red/Pink/Rust-Colored Sputum

Pink to red sputum color is usually indicative of the presence of blood in the sputum. Blood cells may cause complete discoloration of your mucus or appear only as spots or streaks. Pink sputum means that the bleeding is in smaller quantities. Rust-colored phlegm may be due to the breakdown of red blood cells. Conditions with pink/red/rust-colored sputum include:

• Pneumococcal pneumonia
• Lung cancer
• Tuberculosis
• Pulmonary embolism
• Chronic heart failure with pulmonary edema
• Trauma to the lungs
• Pulmonary embolism
• Lung abscess
• Bleeding disorders
• Tropical eosinophilia

Blood in the sputum (hemoptysis) may be a sign of some major illness for which you need immediate medical attention. If you cough up a lot of blood with mucus, immediately call emergency services.