Fresh shrimp is blue and white, but it turns bright red after cooking, which is caused by a substance called “prawn erythroin” in shrimp. Astaxanthin is a kind of carotene. When cooking at high temperature, astaxanthin will be quickly decomposed from the shrimp body. Therefore, the original green white shrimp will become bright red. Because the distribution of prawn erythropoietin in shrimp is not uniform, generally the back is the most and the abdomen is the least, so the cooked shrimp has the reddest back and lighter abdomen color. However, because the astaxanthin in shrimp is not stable and will leak out, live shrimp sometimes show a bright red.