The color of the pleural effusion alone cannot accurately determine the benign or malignant nature of the pleural effusion, but also needs to be combined with the volume of the pleural effusion, other components, and symptoms in order to make an accurate judgment. In general, non-haemorrhagic effusion is mostly considered to be benign. 1. Clear or yellowish pleural fluid is leakage fluid, which can be caused by heart failure and hypoproteinemia; straw yellow pleural fluid is exudate fluid, which is often caused by tuberculosis. 2. Celiac pleural fluid is caused by obstruction or rupture of thoracic duct or lymphatic vessels. 3. Pus-like turbid fluid is mostly infected, green slurry in Pseudomonas aeruginosa infection, and chocolate-like purulent pleural fluid is characteristic of amoebiasis. 4. The glittering ichthyosis within the pleural fluid is cholesterol pleural fluid, which is seen in encapsulated effusions (often tuberculous) with a long course of the disease. 5. Hemorrhagic effusion may be tumor, tuberculosis, ruptured aneurysm or puncture injury. Abnormal pleural effusion, should actively consult the doctor, the doctor according to the specific conditions of the corresponding treatment plan.