You would have to strip out the old colour first and then re-dye to get a uniform colour, otherwise the lighter patches will still be lighter. If actual bleach is what has removed the colour in the first place, it still may not dye. I took apart a dress to redye part of it which worked well but it was a cotton type fabric. I have a rayon dress I need to do the same thing to sitting around waiting for me to have the time. Good luck!