Hi, I think not any relationship between pigments in raw milk .

The main reasons of red color in milk  is Mastitis  

The significants of knowing the colour of the milk:

1-     To detect any abnormal colour of milk as in mastitis.

2-     Certain bacteria produce pigments in milk e.g.

              Pseudomonas synxanthaproduce yellow pigment               Bacterium erythrogeneproduce red pigment

It may be due to rupture of udder capillaries in fresh cows/heifers. There is no relationship with alfalfa.

I agree with previous answers

The main reason of red color in milk  is acute Mastitis  

Other suplementary reasons

1.alfalfa hay may be rich in coumarine, especially if contaminated with molds

-2 alfalfa hay may be rich in fitoestrogens, inducing hyperestrogenism and a possible fragilization of blood vessels from genital organs

Thanks to all