Here are my guesses:
Possibility #1: The first farm may have milked Guernsey type cattle - "Golden Guernseys" are known for their richly yellow-gold milk. This is because they produce more beta-carotene, and vitamin-A precursor, and which pigments the milk, and especially fat (cream) yellow. If not Guernsey, then perhaps Jerseys - heavy cream producers, which might cause the early separation of fat from milk. The second farm, by contrast, might have another breed, probably Holstein, whose milk is lower in both fat and protein. This also explains why the pH seemed to drop quicker: milk protein (casein) buffers acidity; with less casein around, acidity will rise faster. You would probably also notice a reduced yield with second farm's milk compared to the first's.
Possibility #2 (mostly in regards to yellowness): First farm grazes their animals more, feeds more hay and alfalfa, and less or no corn or grain. Again, the yellow coloring comes from beta-carotene, and green feeds are higher are in this than the more starchy, less nutrient-dense corn (silage or grain). Also, feeds with long fibers contribute to higher fat levels in the milk.