the size of eggs goes up as the hen gets older. When a pullet starts to lay her eggs are smaller than her older sisters, as she gets older they get bigger. Commercial hens are replaced as they reach 18 months, many people are rescuing them so they have a chance to live out their days in a happy place, some of the poor chickens are oven-ready, their feathers have been pecked out because hens need space and they are crammed in unacceptably. Some don't survive sadly but those that do often have a happy few years, and continue to lay eggs. Colour depends on breed. My little bantams lay creamy coloured eggs. Sometimes with brown freckles on. They are all different colour hens, all the same breed, some are black, some brown, buff,some golden, some lavender. popular IIRC because people thought they were better for you. Well TBH the shell colour is irrelevant, yes, look at their ears and their ears are the colour of their eggs generally. Some breeds lay green eggs some blue. All the same colour inside. I have different colour hens just because they are pretty. Hens spend hours every day pecking, they peck at little insects, at food, at plants, it's a natural behaviour and idf they can't peck for food they peck each other. Support your local chicken keeper and knnow that you are supporting happy hens whatever colour eggs they lay if you can! Or consider whether you could keep a few yourself, they are so soothing to watch as they scratch and peck, and cluck happily away to themselves