Unfortunately there is no way to re-dye a saddle...I actually did some research into this years ago because I had a tan saddle I wanted to dye black. Coloring the leather is actually a middle-of-the-process step: other things are added once the leather is colored to seal it, thus you can't put new dye on and have it "stick". Admittedly, if the dye is coming off yours, it doesn't sound like it was well-cured, but I can't imagine you would end up with anything other than an uneven blotchy mess.