I think it depends on how dark you want the marble. If its red iDye, this takes a lot quicker the red RIT. I did black SC paint (I would guess similar times to) over vinyl on proton plastic and needed 24 hours plus to get the full dye. On the same disk I wanted to do get grays (to get smoke) and did 3-6 hours depending on how dark I wanted it. If you want it dark you may want to wait until tomorrow morning. If its just giving texture to to the blank spaces, you could probably pull it this afternoon. If you think it's too light, you could probably just throw it back in for longer time and have a few different shades of red!