How does a brown cow eat green grass produce white milk and yellow butter?

A brown cow eats green grass, which is rich in nutrients. The cow's digestive system breaks down the grass, allowing it to absorb the nutrients and convert them into energy. This process leads to the production of milk, which is typically white due to the fat and protein content. When cream from the milk is churned, it separates and creates yellow butter, primarily influenced by the cow's diet and the presence of carotenoids in the grass.