Probably the greatest confusion for clients is when they have the same color, but in multiple Design Locations. An example is a client may look at their project and see that they have Gold and Navy in a Design Location on the front of their selected product (e.g. t-shirt, hoodie) and then Red and Navy in a Design Location on the back. So they figure that they have Gold, Navy, and Red or they determine three (3) colors in their project.
Unfortunately, they really have four (4) colors in their project and will be greatly disappointed when they actually get their quote for more than they thought it would be. The reason they have 4 colors rather than 3 is that the Navy color in both the front and back Design Location are considered two (2) different colors, even though they are both Navy.
The reason for this goes partially back to the definition of Design Locations explained in the How is the Price for Screen Printing Computed? article. When we print the front Design Location we have to generate film/screens for both the Gold and Navy colors (See the What is Screen Printing & How Does It Work? article for more information on how screens are created), then setup the press aligning these color screens for that specific Design Location. Then, after the press is setup and we have run test samples to make sure it is setup correctly, we would print the front design location. After we had printed and dried all the products with the front design location then we would tear down the press (take the screens down, clean the ink out of the screens, and clean up the press). We would then set the press up again for the back design location, just like it was a separate job. This would require a different film & screen, printing, etc. for the Navy color in the back design location from what was printed in the front design location.