CoffeeGuy said "It was my understanding that a dark yolk is ideal because it is an indication that the chicken received proper nutrition "
While the colour of the yolk is an indicator of their diet, it doesn't mean it's "proper nutrition" (although I would assume all egg producers give their hens the best diet possible in their circumstance). The colour can be influenced by the type of feed (corn vs. wheat, for example), but can also be manipulated by non-nutritive additives like marigold petals.
One thing for certain, that if a hen is eating their natural, omnivorous diet, which i:ncludes bugs and greens in addition to their grain, their yolks will be naturally darker. BUT, because the colour can be influenced independently of that via additives, you can't rely on that as an indicator unless you KNOW the hens are allowed access to the outdoors and permitted to forage, i.e. from a small producer selling from a farm gate in all likelihood.
All eggs, regardless of how they are produced, have fundamentally the same nutrition, with small variations in the micro-nutrient levels. In mass-produced eggs, from a marketing standpoint at least, the biggest factor for colour is simply visual appeal.
https://www.rd.com/article/egg-yolks-different-colors/
https://www.organicvalley.coop/blog/what-does-egg-yolk-color-mean/