nostr:npub1kc8ctl9ccyaqklpwzaqrllvt5j0dpdyd6clltqqf6dp9yzkchy3qnaj65c I don't know about this and the probiotics. Eggshell color is somewhat different of course breed/genetics mostly - but there's enough supplements (probiotics or other 'natural substances') in feed to affect characteristics. Yolds here all have a yellow/orange hue (besides the flavor).
I'm sure they are fed a 'good' diets (not pumped up like factory farmed chicken in the US) - but even so, I'd be surprised if there wasn't some added beta carotene or other yolk color enhancing element here