Do the crop marks in the imposition scheme created in eDoc have a CMYK value?

The crop marks are in the special PDF color "ALL". For a PDF using the standard CMYK model, this makes them appear on plates C, Y, M, and K. If the PDF were using strictly RGB, they would appear on plates R, G, B. If there are spot colors, they appear on those plates as well. It automatically adapts to the color model used by elements of the PDF. This is standard built into the PDF file format.