Different colors of pleural effusion reflect the cause of pleural effusion disease, the nature of the disease is also often different, so to some extent you can observe the color of the pleural drainage fluid, the cause of pleural effusion to have a general judgment. Common colors of pleural drainage fluid are: i. Red. When there is bleeding in the chest cavity due to trauma, bleeding, tumors, or other causes of bleeding in the chest cavity, the color of pleural fluid is darker red, and the more bleeding there is, the darker red and heavier the color. Second, white milk, white. In various post-surgical, post-traumatic and other cases, when the color of pleural effusion is white it often suggests thoracic duct injury and the formation of celiac chest. Third, grass green. If the color of pleural effusion is grass green, there may be tuberculosis infection in the chest cavity and other conditions. Black color. When the color of the drainage fluid in the chest cavity is dark, there may be mycobacterial infection in the chest cavity.