In the grocers, look for eggs labeled PASTURE-RAISED, such as Vital Farms. Pastured hens live outdoors in movable coops.
In a Farmer's Market, ask the seller "what do you feed these chickens?"
Eggs that are colored, speckled or slightly dirty don't mean the birds were pastured. They may have been raised in a fenced dirt area with no access to bugs or forage. Eating GMO corn and soy - not a natural diet for birds.
Pastured chickens' natural diet is bugs, green plants and seeds. When insects and seeds decline in the winter, they need a grain mix in addition to most any food products from the farm.
Chickens are NOT vegetarians.
Full Notes at
https://www.ondietandhealth.com/healthier-ways-to-buy-and-eat-eggs/