The pnimius is also meorrer the chitzonios.
Is my sons high school, the Rabbeim watch closely those who decide to wear only white shirts, and very often after observation discourage cetrtain boys from doing so. The official yeshiva dress code allows for blue and pinstriped shirts.
Wearing a white shirt announces your affiliation, the same way, lihavdil, wearing a baseball jersey announces the team you like to follow. Wearing the uniform does not you a member of the team and wearing a white shirt does not make you a ben torah. In the minds of many, since the outside impacts the inside, it stands to follow that wearing a white shirt makes one a ben torah and baal middos.