Every Jewish women is about to be wearing a white skirt & white blouse, 4 times in the next 3 months:-
1) Chamisho Ossor b’Ov
2) 1st day R’H
3) 2nd day R’H
4) Yom haKippurim
BTW I am referring to the last Mishno in Taanis {1&4} so it is absurd to refer to white clothing as ostentatious.