Yellowness of egg yolk Related question: Why are Italian eggs so yellow?

Occasionally I get served a fried / poached egg with a deep yellow/orange yolk. I find it extremely appetising and visually attractive.

Sometimes eggs have very weakly coloured yolks, which is less appealing -- but I couldn't swear that the flavour is affected.


Is there a correlation between the colour of a yolk and its flavour?
When shopping, how can I increase my chances of getting a richly coloured yolk? 


Does free-range / barn / battery make a difference?
Is there a correlation between price and yolk colour?

Do egg producers and/or chefs use dirty tricks to effect a yellow yolk? Dye? Food additives?


I'm in the UK, but please feel free to give answers for other parts of the world. If you suspect they're not universal, make sure you point out your location.
Regarding the last question:


  Do egg producers and/or chefs use dirty tricks to effect a yellow
  yolk? Dye? Food additives?


Yes, they do!

In fact scientists have experimented with food additives in order to control the color of the yolk. Interestingly enough the preferred color of the egg yolk differ between countries and even between regions within countries.

One study examined the red and yellow additives from marigold flowers and paprika fruit.
Note that artificial coloring additives are banned in the US, thus the interest for natural colorings.

Details can be found in: Egg Yolk Color as Affected
by Saponiﬁcation of Different
Natural Pigmenting Sources