are you talking about swirling ??? kind of confused as to what you are asking? do you have a pic for an example of the effect youre trying to achieve? we could better answer you with more info!
ok sorry, I meant swirling. I've seen it demonstrated on teachsoap but they don't say clearly what they use for color. Is it a liquid added to half a batch at trace and then 'swirled' together in the mold?
ps how do you add an image here?