Color Printing Specification

There are two methods of specifying color for printing: process color and spot color.

Specifying process colors - Process colors are generally specified as combinations of cyan, magenta, yellow and black (CMYK, K for Key). CMY process color is used in some desktop printers and can be used on a press with only three printing units like the Mark Andy Flexo press in our press room or the new ComCo Commander. The process colors can be printed as solid or as tints of specified percentage. The process colors provide a large palette of colors.

Tint combinations involving three or more colors are difficult to control. Any three color tint can be matched using two colors and black, which is easier to control. The amount of dot gain (increase in dot size from the specified value) can vary widely for different presses and papers. Prints on coated papers exhibits low dot gain and appear cleaner and brighter, while on uncoated papers the dot gain is higher and colors appear duller.

Digital tint generation allows precise selection and full control over dot size and shape. Several process color tint selectors are available with printed samples. These include PANTONE (available in both SWOP and Eurostandard versions), Focoltone and TRUEMATCH (includes samples on both coated and uncoated papers). Extensions of the process colors which employ 6 or 7 colors are now available. (e.g. PANTONE hexachrome)

Specifying Spot Colors - Spot colors are obtained from a set of intense , saturated base colors. Such colors are used extensively in advertising and product packaging, where brand identification and logo recognition are important. Spot colors are also used in combination with process colors. Spot colors are generally opaque, so that overprints should be avoided.

When to use Spot colors: Jobs not printed in CMYK. Use only 2 or 3 colors and do not contain color pictures. Cases where color matching is essential, e.g. corporate logos or product packaging. Improved matching of design elements, e.g. backgrounds rules and borders. Non-gamut colors, i.e. colors not representable as CMYK, e.g. highly saturated colors and pastels. Spot colors can extend the printing gamut.

Printing inks with special optical characteristics, e.g. metallic, fluorescent and pearlescent finishes. Used for greeting cards and gift-wrap printing. Print large areas of solid color. Avoids setoff, tracking and ghost patterns. Can produce smooth flat colors with no visible dot pattern. Replace a CMYK color. Allows better color matching. Color separations must be modified accordingly. Extend the colors available in CMYK, e.g. a bump color to intensify color in selected parts of an image.

The intensity of spot colors can be extended by printing the same image twice, or double hitting the color. This can be very effective with fluorescent colors. Standard spot color systems include the PANTONE Matching System (PMS), Toyo 88 and the Munsel system. All of these are supported by PageMaker and all but Munsel are supported by Photoshop and Illustrator.

Color Matching - When a color is required that does not appear in one of the standard systems, it is best to select the PANTONE or CMYK closest to it. If a physical sample is available, the CIELAB coordinates can be measured and the nearest CMYK identified. Some software matching systems are available. The PANTONE Hexachrome (CMYK + OG) system can match 90% of the PMS colors.