What's the Difference?
In the world of desktop publishing, the differences between spot color and CMYK lead to a number of traps for the inexperienced designer.
Corporate designers with big budgets often mix spot color with CMYK to achieve special effects. Metallic and fluorescent spot colors added to a CMYK mix are prime example. When this is done unintentionally, it's a recipe for disaster. If the job is a four color job and a Pantone is inadvertently inserted into the mix, one of two things will happen. The first option is that the printer will create a fifth plate, and then run the job through the press to add the additional Pantone color. The problem is that the process results in unexpected expenses. The second option is dropping the Pantone plate entirely, which will result in missing text or graphics in the printed product.
On the other side of the spectrum, when a spot color job is created using CMYK instead, four plates are created to simulate the spot color, instead of a single plate. The result is budget headaches and printing delays.
An added problem is that design software is picky in how it deals with the naming of spot colors. While you may think that Pantone 123C is the same as PANTONE 123c, the software might disagree. Differences in capitalization might indicate two different colors, which leads the printer to create two different plates (resulting in more budget overruns).
All of which makes the difference between spot color and CMYK not just a design factor, but a dollars and cents factor as well. As you now understand, learning about the printing process is time well-spent.