Quote Originally Posted by lstsl View Post
Hi again, I would just like to clarify something in my previous statement. The phenomenon where an object appears to be blue when headed in the opposite direction of the observer when traveling at near light speed is called "blue shifting". It occurs because blue light travels faster than red light, and as the object is moving farther away, the blue light begins to outpace the red light by an even greater degree. Usually viewed as galaxys zoom about the universe, but the same should hold true for apples as well.
I think you have this reversed. Objects which are approaching the observer appear bluer, while those receding appear redder. And this is caused by frequency shifting, not by velocity. The speed of blue and red light in a vacuum are the same. As an object approaches, the light waves are compressed and the light seems blue, just as when a train approaches the sound waves are compressed and the pitch of the whistle is higher. With light receding from you, the frequencies are "stretched", causing the light to appear redder (red-shifting, in astronomy), just as the train whistle's pitch gets lower as it recedes.

See http://en.wikipedia.org/wiki/Doppler_effect for a fairly simple explanation.