Learn more about fat colour
The major fat soluble compound that accumulates and causes yellow fat is ß-carotene. The transfer of cattle from fresh pasture to a grain diet reduces the ß-carotene concentration in blood serum and the fat will not continue to increase in yellowness.
Seasonal and climatic changes in fatty acid composition can occur in beef carcases. Temperature and rainfall are likely to affect fatty acid composition in several ways. Firstly, there may be differences in feeds (or feed quality) from one season to another, although that is likely to be more of an issue for pasture-fed rather than grain-fed cattle. Secondly, changes in fat composition result from established climatic differences (colder versus warmer regions).
The following resources provide more detailed information about fat colour: