Our new members wear all white "dressy" clothes, which permits slacks as well as skirts and dresses. We're not overly fussy about the pureness of the white, though, so we get a lot of variation. After all, it's tough to find true white when your pledge class is initiated in December, as mine was! The sisters (both collegiate and any alumnae who are there) wear all black.
We follow this same dress code when we induct a new chapter. But to go one step further to honor that new chapter, on the day of the induction sisters all over the country wear all black and their member badge in tribute... which we'll be doing tomorrow to welcome our 26th collegiate chapter!!