Refinish speaker in different color

I'll add my vote to those who have said restaining is difficult and not worth the trouble unless you can't get what you want. I spent a good part of last summer breathing toxic stripping fumes, cleaning toxic debis, scraping, sanding, refinishing with steel wool, applying polyurethane etc. If your really in the mood you could attempt it but the black will have penetrated the grain of the veneer in places as mentioned above, making a good outcome very uncertain. If you can tolerate a dark streak here or there and are a real DIY then try it. Realizing you may not get the finish you really want.