Hi PPS Lists, I thought I should respond as the resident expert responded by telling you to do RGB, when your question was about CMYK. The approach you outlined sounds right in principle: create a CMYK image with some overlapping swatches in CMY and K. If the printer processes it as CMYK you will be able to see a difference in the amount of toner / ink deposited in the swatches depending on the mix. As long the the driver doesn't transform the image. Printing CMYK requires Postscript which means the both the printer and installed driver must support it. If the driver is PCL, it's RGB only. I would expect a CMYK image sent to an RGB printer would produce an error, or just produce a blank area for the image, but not sure. If the printer is Postscript, it can take either or both forms of data at once. You may need to select print dialog options pertaining to color to ensure the data are not massaged. In some devices, it learns what to do from selected ICC profiles. There is lore that says if you create a PDF this can make getting CMYK data to the printer easier. This discussion considers some gotchas from an Adobe perspective. https://community.adobe.com/t5/acrobat/printer-color-management-is-not-passi... Save CMYK as PDF from Illustrator https://graphicdesign.stackexchange.com/questions/81048/how-to-save-as-adobe...