Leather will shrink a little, but there are some rub on dyes that will work better.
The dye job depends greatly on what kind of fabric the suit is made of. If its cotton, or mostly cotton you have a great chance. If its polyester, you have an uphill battle.
Whatever you do, make sure you wash the clothes first and make sure its thoroughly wet before you put it in the dye bath or it won't set evenly.
Also, check it for color fastness when its done or it will come off on whatever shirt is underneath and possibly the figure itself.