It's to do with diet. IIRC, some farmers feed their flock flax in order to get more orange yolks. But free range hens that have access to insects tend to have a nicer flavour in my experience. Generally speaking, an egg with a hard shell and a very bright yolk will be nicer and that tends to correspond with free range hens. But, climate where you live will influence how realistic that is.

If you're lucky, your friend with chickens might have blue-green egg shells.

You can buy eggs with blue shells and bright orange yolks in UK supermarkets, I ate some yesterday.