Farm eggs will often have brighter colored yolks-all depends on what they are eating. And yes, fresher eggs are harder to peal.

You can also get "flavored" eggs if the chicken gets sprayed by a skunk, or eats different types of weeds if they are free range. The eggs can literally get a "weedy" taste to them. (So can milk if the cow eats certain weeds)

I grew up on a ranch and we always knew if a skunk had gotten in the chicken coop :-)