The infection was usually found in either your groin or armpits. After that it spread to your thighs and arms.
The parts that are most exposed to the sun which usually is the arms, legs, and face.
Colorblindness would be a retinal deficiency. In particular, the cones of the retina do not detect the colors that typical cones can.
If vampire movies are to be believed, then the neck. Generally, they aim for parts that have maximum blood vessels in them.
I'm not an expert, but I would assume it would be the ankle or the knee since those are both smaller joints that are subject to a lot of pressure, strain and torque during a most sporting events.
Bionic Body Parts
The Body Worlds Exposition - Part 2/2
The Body Worlds Exposition - Part 1/2
Exercise for the Most Hated Body Parts