Following the given color transformations:
- Blue means green,
- Green means white,
- White means yellow,
- Yellow means black,
- Black means red,
- Red means brown.
Since milk is naturally white in color, according to the transformations:
- White means yellow,
- Yellow means black,
- Black means red,
- Red means brown,
- Green means white.
And according to this transformation, the color of milk is Green.