Hi!
Did a search on Google found a few things:
There is no way to change the color of leather. Even if you bought leather dye, and tried to re-dye the leather in a big vat, it will not look right, and will not remove the original color. You will end up with a blotchy mis-colored surface, and most likely it will turn shit brown. This is because leather is dyed early in the tanning process; once compelte, there is no way to change the color of the hide. You only can dye tanned leather once, and all automotive leather is tanned.
You will need to buy new leather covers. Spray paint will always crack and flake as your leather stretches and bends when you sit on it.
Though found this:
http://www.youtube.com/watch?v=uoJvdEBYIUA" onclick="window.open(this.href);return false;
Lots of things, a search:
https://www.google.com/search?q=changing+the+color+of+leather+car+seats&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=" onclick="window.open(this.href);return false;
Cheers,
Alistair