How can I detect bad-fed or fast-fed chicken eggs before buying?
It's not a simple matter to spot a good egg just by looking at it. Different breeds of chicken will lay eggs that look a bit different from each other. Also, it used to be quite common for farmers to feed the chickens some colourings that make the egg yoke more yellow. So a strong colour inside doesn't mean it's good quality.

I'd suggest, if you think eggs are cheap enough for your to not worry about money, you look for free range organic labels on the egg box. If the egg is officially from an organic source then you know it's not from a chicken stuffed up with chemicals.