Light yellow stool is due to the presence of bilirubin in the stool. Normal stools are mostly light yellow or yellow-brown in color, and the color of the stool may change depending on the person’s diet and physical condition. If you eat too much dark food, the color of your stool will be darker. If the color of the stool is white clay-like, we should pay attention to the presence of biliary obstruction factors, liver function tests can find a significant increase in bilirubin and liver function abnormalities, you can do an ultrasound of the liver and biliary system to facilitate diagnosis. When you have eaten dragon fruit, the color of your stool will be black and purple. If you have eaten too much animal liver or chicken or duck blood, the stool may be black. If you have taken medications containing iron or bismuth, the stool is also black, but when the diet is changed or the medication is stopped for three days, the stool color will be normal.