Why milk looks white
Milk gets its white look from tiny drops of fat and small clumps of protein called casein micelles. Both scatter light. The fat carries a little carotene, so milk from Jersey and Guernsey cows can look golden. Skim milk has lost most of its fat and can look slightly blue. The Wikipedia article on milk explains this.
Where the code comes from
Wikipedia's alphabetical list of colors gives Milk as #FDFFF5, the same as ours, but cites no source for it. The code is a very pale white with a hint of yellow green. It is close to ivory, #FFFFF0, and much lighter than cream. A near twin is lotion.

