The problem with the white shirts is that for most people it might actually be more a chilul hashem as opposed to more “modernish Clothing”
When one is wearing a white shirt with dress pants, the shirt has to be tucked properly into the pants otherwise you look very shlumpy. It doesnt look very refined at all, it makes you look like a slob. Shirts that you wear untucked you dont like a slob.
The other problem with white shirts is if you accidently get a stain on them during the day, the stain tends to be more prominent as opposed to a differnt color shirt where the stain can be obscured or hidden. Going around with soiled clothing does not make a kiddush hashem. even a simple water stain looks alot worse on a white shirt than a blue shirt