Whether a one-and-a-half year old baby is color blind can be determined by observation and medical testing. Generally speaking, a more accurate diagnosis can only be made after the child is three years old or older and has a preliminary concept of color. 1. Observation: Color blindness refers to the lack of ability of the eyes to distinguish colors. Parents can observe carefully to see if their babies can distinguish colors such as red, green and blue through colorful toys and picture books. If a one-and-a-half year old baby has color blindness, has poor perception of brightness and very poor eyesight, he or she should be examined in the hospital as soon as possible. 2. Medical testing: If you suspect that your one-and-a-half-year-old baby is color blind, you can go to the ophthalmology department of a regular hospital for a color blindness mapping test. Children under the age of three often cannot express the colors they see well, so it is not easy to find out if they have color blindness. If parents find that their children have obvious visual abnormalities, it is recommended that they bring their babies to the doctor in time for examination and treatment.