If that sheath came with the Bushfinger at Blade, it's been completely sealed on the inside to prevent the dye from staining the handle.
There had been some problems in the past with this issue, so I've tried to seal everything on the inside. Fingernail polish remover or straight acetone will usually remove minor stains from dye. A little mineral oil or wax will bring the finish right back. Just to be totally correct, that's what I do with mine, but it still is your choice. Bottom line, if you like the sheath, but are concerned with the dye, I'll make another one just like it without any inside dye. No charge and I'll pay shipping.