Purple Prints Navy

I suggest you talk with the painter's tech support. That type problem is a printer problem and not a Mac problem. The Mac just sends the signal; the printer is responsible for interpreting the signal.

It might also be blamed on what program created the images you are trying to print. Which could be why different results are found because the app is configured differently. I.E. - Possibly a hidden layer on the image causing the problem. As a test, you could copy the file that prints the correct color to the computer that doesn't print it right, then test to see what happens. All this is based on my assumption that it might be an image layer problem.