I think kev is being a bit cynical. He could be right in some instances, but there are now plenty of real free range eggs available.
The yolk colour is affected by what the birds eat, and most layer's feeds do include something to colour the yolk.
To answer your question: I think you'd have to be a specialist taster to tell any difference, if there was any difference. I'd say they taste just the same. They do have a different texture, as well though, they often seem much thicker to me. They seem to 'hang together' better when you cook them.