monolithic – wow, do you work for Artscroll? 😉
And no they don’t send the dress code to the parents rather before enlisting into a Yeshiva you should have done a lot of painstaking research to find out that that is the best place for you/ your son to shteig and will therefore know exactly if it’s the norm there to come in with a coloured shirt.
And obviously even a white shirted yeshiva is not gonna kick out any blue shirts, come on, rather a blue shirt will feel uncomfortable (hopefully) surrounded by white shirted yeshivish looking guys…I can’t see a blue shirt wanting to come to a white shirted yeshiva anyways…