It's unlikely you could get the black to white, or even a lighter colour (grey, orange, who knows -- blacks aren't consistent) without damaging the fabric. Bleach is an inexact science at best, and even when it does exhaust colour, it tends to weaken the fabric, especially when industrial dyes (much more colourfast) are used. You'd be better off trying to paint over it with a sufficiently opaque fabric paint than you would trying to bleach it out.
Therese von Ludowing (Sound Horizon's Märchen)Elsewhere: Journal ~ ACP ~ CosplayLab
Catelyn Stark (A Song of Ice and Fire / Game of Thrones)
Ichihara Yuuko - butterfly kimono (xxxHolic / Tsubasa Reservoir Chronicle)
Elisabeth - red ballgown (Elisabeth - Takarazuka version)
Thessaly (Sandman - The Kindly Ones)