i have seen a lighter portion of an orange, but not evenly. if i'm not mistaken, shaded area on one side will give you that effect. or maybe bleach? or maybe photoshop? hehe ..
I seen those oranges like that before is just that one side always have the sun and the other side never do get sun or hardly that is why it the color of the orange looks like that... But i wonder how the orange would taste... hmm...
you can do that at home i think just wrap up a not quite ripe orange on one side stick it in a sunny area and let it rippen the wrapped side shouldn't rippen as well, leaving it lighter
either half of it has been exposed to the sun while the other side was not. It could also been a GM orange. If it's the case, I'd stay clear as it has dreadful chemicals!