Cows spend all day, and more, eating grass...............

[Auric Goldfinger]

............so " Why isn't milk green ?? " And beef come to think of it..............

[2SkodaFamily]

You really need more to do........

[FellyMagic]

He has a lot to ponder as he drives his bouncy spam tin all day...

[devonutopia]

Because the "green" nutrients are converted into milk nutrients by said cow. That's why the **** is brown as that's what's in the green stuff, once all the green stuff is extracted by the (several) guts.

What do cows drink?

[Kablam]

MILK!! oh wait...