I have a pair of shoes that are red that I want to wear to work but I can only wear black shoes to work. They are leather and I want to dye them black. I don’t want to use spray paint or anything tacky, I want them to look like they were meant to be black.
Unless you already you give them a shoe repair professional, you won’t able to do it.
As I read the other answers, it seems nobody brought the main answer which is they have to be bleached back to the original leather skin color. The professional will basically have to take away all the red dye first. THEN he can dye them in black.
Otherwise, let’s say you use black shoe polish over the actual red color, it will result a nice mess.
Try to find a shoe repair person who actually works leather or ask him/her to give you a reference in your town.
Good luck!