It depends on the diet, as Thomy says, which also depends on the time of year. Spring is the best time for eggs.

Really dark orange/red yolks indicate lots of insects and worms in the chicken's diet. Unfortunately that doesn't happen very often.

The pastured eggs I get are also soy free and rather yellow. I guess the chickens still get lots of grains.

But much better than soy, if I eat eggs from soy-fed chicken, my body will be covered with countless red spots on the next morning and it feels like having slept on an anthill ;)

This is slightly off-topic but was quite interesting for me to hear:

My uncle is a Dr in genetics and did a lot of allergy research, for example, they tested the impact dairy and different kinds of eggs (organic, cage,..) have on conditions like atopic dermatitis, hay fever and so on.

What they found was that when it comes to allergies, there was no differnce between cage eggs and organic eggs, but he said there might be other health benefits that they didn't look into.

see the research on soy-free eggs: http://www.grassfedtraditions.com/organic_soy_free_eggs.htm#Research

It took me years to find out wghy I couldn't eat eggs any more until I found out All eggs get feed soy . I mean all eggs! Doing research I found out they all buy the same feed for the chickens because soy is cheaper corn is more expensive nowadays so they sell these vegaterian eggs as a positive and the only diffrence with the organic eggs is the soy is certified organic it's actually from the same guy but sells the feed for more money ! it's the biggest scam I have ever seen . The eggs in Win Dixie are feed the same as all the brands in whole food ! Crazy!