Shabbos Clothes

Why do Ultra Orthodx people where black on Shabbat?

Shalom!

Thank you for your question.

You are correct that most in the ultra-orthodox emphasize black and dark colored clothing both on Shabbos and weekdays, and yes, even more common on Shabbos.

Interestingly, however, earlier sources seem to imply that white is the preferred color for Shabbos clothing. So how, when and why did things change?

So why did things change?

Some explain that dark colored clothing conveys dignity, and Shabbos is a day on which we are to look more dignified. Indeed, litigation lawyers in Israel are required to wear a black suit and white shirt when in court. It is also the color of judges’ uniforms worldwide. Non-Jews wear dark colored suits to funerals and other more formal events. As such, we can see why dark colored clothing would be appropriate for Shabbos.
Ultimately, there is no true color requirement for one’s Shabbat clothes. More important than the color is the requirement to have clothing reserved exclusively for Shabbos wear. This is true regarding one’s outer clothing but one need not have undergarments designated specifically for Shabbos.

It is also commendable to have a special pair of shoes for Shabbos though it is not truly required as shoes are not truly considered to be “clothing” from the perspective of halacha. One who must wear his weekday shoes on Shabbos should clean and polish them each week before Shabbos to ensure they are clean. With the exception of a Brit (and some include a wedding), one should not wear one’s Shabbat clothes on ordinary weekdays.

Rashi to Kiddushin 72; Shabbos 113a; OC 242, 262 with commentaries; Rema, OC 551:1; Magen Avraham, OC 262, 597; Elya Rabba, OC 262:4; Be’er Heitev, OC 262; Kaf Hachaim, OC 262:4; Aruch Hashulchan, OC 260:1; Mishna Berura 242:1,5