A brand in the UK called Clarence Court started producing a range of eggs (maybe a decade ago?) that have an intensely orange yolk [1] and this became a real differentiator, in some ways an indicator of quality. I know when an egg is Clarence Court in a restaurant for instance (and have confirmed numerous times). They are also delicious eating.
The effect is so profound that supermarket own brands have now also started producing similarly richly-orange-yolked eggs.