Buzzfeed has a series of black and white photos that have been altered to show how they would appear if they had been taken in color.  There are several that are more powerful to me in color than in the original black and white, but there are also a few who seem to lose some of their effect when translated into a color picture.  Follow the link to see them.  This one of President Abraham Lincoln is the most powerful to me.  Seeing him in color makes him less a historical figure, and more a real man.