Abstract: A color referencing system is provided whereby a process color is first defined in terms of percentage levels of a number of base colors to create a standard reference, an ink mixture is experimentally defined for a flat color which corresponds in appearance to the process color and the CIELAB or other color difference equation value is determined by conventional means for that matched color. Such a system is only possible if the process color reference standard can be repeated without error. The illustration of the process colors in relation to their standard reference is therefore ideally achieved by the system as is defined in European Pat. No. 0119836. It is then possible to start from a flat color produced by single ink printing and reproduce this exactly as a process color by a predetermined combination of four colors using particular screened percentage values.

Abstract: Colored art work is produced by the use of a kit comprising a collection of small process color reference "tints" printed from selected combinations of three standard process colors, optionally with black, at selected percentage densities. The reference tints are arranged in groups with all the tints in one group having the same percentage, but varying combinations of process colors, and each of the tints is identified by a reference index. The kit also includes larger "cut-out tints" identifiable with individual reference tints and each of exactly the same tone as the corresponding reference tint.