He is blue throated, not blue bodied, which is depicted as FAIR, gaur varna in Sanskrit.Shiva, the Destroyer, is also depicted in light blue tones and is called neela kantha, or blue-throated, for having swallowed poison in an attempt to turn the tide of a battle between the gods and demons in the gods' favour.
Scions of well to do families are not born prison cells, as He was.He is blue because he was born with a silver spoon in the mouth...as most well to do families then used silver as plates/bowls/utensils. Something must have gone wrong where the little Krishna ingested silver....
OR...he could have been an Andorian (StarTrek!) kid hiding on Earth from those interstellar wars...you know, Indian stories are full of them....
My bet is the silver poisoning...and it is permanent....