tzippi- correct. Joseph did not mean that one who doesn’t have this “uniform” is not fit to study or learn C”V rather it is accepted in most Yeshivos to have a dress code and Bochrim are definitely in Hashem’s Army…
Regarding the whole issue I think anything that strays from the truth is Ossur and everything which doesn’t is Mutar- foolproof!!! If the Yeshiva DOES have some blue-shirted Bochrim and they want to delete him because they feel people will give less to that kind of Mosod then it is definitely wrong to take him it because it is straying from the truth.