How Photoshop Spot Colors Print

By default, spot color channels created in Photoshop will overprint on all the other color channels above them in the Channels palette. If you are printing more than one spot color from Photoshop, you can control the print order of the colors by changing their order in the Channels palette. Lower channels overprint all channels above them. If you would like the spot color to be knocked out instead of overprinted, simply make a selection of the channel object you want to knock out, activate the proper channel, and then press the Delete/Backspace key. The selection will be knocked out from all channels you have selected. Activate the individual channels to view the knockouts.