In 1955, James Dean not only played a major role as Jim Stark in Rebel Without A Cause but also in the popularization of the white t-shirt. Dean's character Jim made the blue jeans and white shirt look iconic (cue Lana Del Rey). Teens all over America could relate to Jim for his angst and daring demeanor, and tried to emulate the rebel by wearing white t-shirts too.
At first glance, a colorless tee doesn't appear to evoke rebelliousness. However, in the 1950s it did exactly that. Simply donning a plain white tee as outerwear was an act of rebellion in and of itself because typically the shirt was worn as men's underwear. Plus, colorless clothing allowed one's true personality to shine through, which in the case of Jim Stark and even James Dean himself, screamed rebel.