This article of clothing is one of many others once owned by a scientist named Dr Hap P.Y Man.

Not much is known about him , any documents of his identity were destroyed after the incident.
He invented clothing that used nano bots (powered by sodium bicarbonate a.k.a soda ) that secretes photochromic dye to change the color of the clothing according to the wearer's surroundings.

This invention was top secret and only the military knew of its existence...until now.

The purple color was caused by the effect of the radiation on the photochromic dye. The lack of sodium bicarbonate had also caused the nano bots to stop working