After applying dye, let it dry 24 hours, buff off the dyed area until no more comes off, your white rag stays white. If you used Tandy's ecoflow stuff, it is water based and many solvents will loosen it up and mix with the solvent (that is in your paint). So as mentioned above, it may need to be sealed before adding the paint.
Do some testing on a scrap piece of leather, same type as you are using.
Tom