I'm currently designing a large print project (200+ pages) that will be printed both commercially in full color CMYK and in grayscale on photocopy machinery.
Is there a palette of CMYK spot colors that I can use that will still hold up well as separate and distinct shades when the product is printed in photocopy grayscale? As many as eight spot colors are needed.
Interesting question. I don't know of any spot color libraries which were created specifically with conversion to grayscale in mind (there could be), so you might need to do some of the leg work manually beforehand. If it were me, I'd probably approach it something like this. Generally spot colors are expensive so you only have a limited number you work with. I don't know how many you'll have in your case but I would want to create some kind of cheat sheet for the project so to speak. I would create a series of swatches based on the number of spot colors you have to work with, choose ones that meet your criteria for CMYK and then convert them to greyscale to see how well they hold up as grayscale. I'm a Photoshop user so would be inclined to say use a Pantone library for example and toggle back and forth between the Color Library and the Color Picker. After selecting a color with the Color Picker and then switching back to the library it should give you the closest match. You can select the a or b within Lab to maintain the same tonality when adjusting the slider. A lot of the Color Libraries are structured light to dark so you could work your way through the range based on your number of spot colors. That would be my approach.
Eight spot colors sure seems like a lot. Unless you have really strict color requirements you might want to just consider printing CMYK rather than so many spot colors. It might give you more flexible color options and be much less expensive. You might want to discuss it with the printer.