Of the constituents of milk, the proteins and fats are responsible for its color. Minute particles of protein are evenly dispersed through the milk’s water content. Each of these innumerable particles causes diffused reflection of light, giving milk an opaque, opalescent color.
The slight yellow shade is caused by carotene found in the fat globules of milk.
Milk from cows whose diet includes pasture grasses rich in carotene has a more noticeably yellow shade.