Have you got a source for that? First result on google indicates otherwise http://www.backyardchickens.com/a/egg-color-chart-find-out-w...
http://blog.chickenwaterer.com/2013/03/influencing-egg-yolk-...
The shell appears to be genetic: http://msue.anr.msu.edu/news/why_are_chicken_eggs_different_...