When sous viding a steak, lets say at 130F for 90 minutes, the steak will be completely red on the inside. However, the steak will look a pale gray on the very outermost portion. The point of sous vide is to get the temperature throughout the meat to be even with the temperature of the water, so it shouldn't go above 130F. I didn't take a picture of my steak specifically, but the picture below is reasonably accurate to what I was seeing.
What is the difference in the meat on the inside vs the outside if it is not the temperature? Why is there this difference in color?