When Do I Need to Create Multicolor Profiles?
Your need for mulitcolor profiles (CMYK + additional channels) will depend on the way that you are separating your files. If you are just working with CMYK builds and a spot "plate" for logos and other vector elements, you will only need a CMYK profile because the spot channel is handled separately. If you are creating multicolor separations, where you are building your colors out of something like a hexachrome configuration, you will need the ability to create multicolor profiles.
