I do not yet know of any slicer that is capable of doing that. i have had contact with a few people who say they can make one and are willing to do so. So I do have a plan for when I am ready to print in full color. There is only one issue so far.
There is no CMYK printhead that we can use for the next 3DP printer. Until that problem is fixed, there is no real incentive to make a full color slicer. If you do find something on the internet, please let me know, it could be useful.