Idid a Google search and came up with this:
http://www.whfoods.com/genpage.php?t...dspice&dbid=37
From the bottom of the above link:
Oranges do not necessarily have to have a bright orange color to be good. In fact, the uniform color of non-organic oranges may be due to injection of Citrus Red Number 2 (an artificial dye) into their skins at the level of 2 parts per million. Whether organic or not, oranges that are partially green or have brown russetting may be just as ripe and tasty as those that are solid orange in color.