Corn and pepper are common foods, but people have found that they have many extraordinary things. Besides the benefits of various nutrients to the human body, the food coloring contained in the product has attracted the attention of many researchers around the world. In corn, there are yellow pigments; in pepper, there are red pigments. These two food colors can be widely used in the coloring of foods such as margarine, candy, and pastries. What does this passage mainly talk about? ['Benefits of Corn and Pepper.', 'The extraordinary use of corn and pepper in scientific research.', 'Nutritional value and attractiveness of corn and pepper.', 'Food coloring contained in corn and pepper and its application value.']