This dye powder is an example of a spot color. If your mixed the dyes, that would be an example of a process color.

While you may not be familiar with the term spot color, it may be the more widely used of the two in the sign and screen printing world. This is because the majority of simple signs produced are made using self-adhesive vinyl, which is a spot color media.

There isn't an actual book definition for spot color, but basically it means that the color was pre-manufactured at some point. Some examples of spot colors include a bright pink house paint, a golden yellow screen printing ink, and a sapphire blue vinyl color.

But what is process color? Process color, on the other hand, means the four colors of yellow, black, cyan and magenta are mixed by the inkjet printing device in different percentages of dots to create a full range of colors. Inkjet printers produce images using process colors. Most often printing presses that print full color magazines and brochures are printed using process colors.

Traditionally, spot colors using vinyl sheets are ideal for digital inkjet sign printing for a number of reasons. First, spot color is a solid color, whereas process color must mix a series of dots to create certain solid colors. Process colors are also unable to create all colors, so spot colors can fill in where process colors are weak. Spot colors can also save on time and materials. Sometimes you will see a vehicle partial wrap featuring vinyl spot colors mixed with digital printing, using the strengths of each to communicate more effectively.

Digital sign printing using process colors is coming on strong. It can make thousands of colors by simply changing the concentration of the four main colors: yellow, black, magenta and cyan. Process colors can be easier to match than spot colors, reproduce images (especially photographs) realistically, and combine to make new colors. 

Ideally sign makers should have the knowledge to know what prints their inkjet printers can produce so that they can set the expectations of their customers accordingly. And of course they would want to use process colors to create the best looking signs possible.