Butter Is Yellow For The Same Reason Carrots Are Orange - Tasting Table
Briefly

The varying yellowness of butter is attributed to beta carotene, the pigment that comes from the grass that the cows are fed, influencing its color.
Grass-fed cows produce butter that is generally more yellow because they consume more beta carotene-rich diets compared to those fed grains like corn or soy.
While the color difference may not significantly impact flavor, it does reflect the nutritional benefits, with more beta carotene translating to more vitamin A.
The richer color of butter is closely tied to farming practices—grass-fed cows contribute to more vibrant butter, making it a reflection of quality in dairy.
Read at Tasting Table
[
|
]