In this paper, we present a rationale for the development of custom colors by blending selected single pigment jet inks. One of the routes to special or custom colors is to blend existing single pigment inks. This approach offers advantages but also places unique demands on the formulation. For example, all of the inks must be mixable in all proportions without affecting jetting characteristics and stability. After good primary colors have been selected and qualified, then commercial spectrophotometers and software are available for suggesting ìrecipesî for particular color inks. This hardware is extremely valuable but is limited in its ability to accurately predict the color of printed images. Examples of well and poorly matched recipes will be discussed. It is necessary to relate the color from ink fills to that printed by the specific ink jet printing system. We will discuss how special colors can be formulated in the lab and approaches to make this practical in an industrial or commercial environment. There are opportunities for increasing the gamut and range of blended colors in a digital printing system. One way to accomplish this expansion is to use additional single pigment inks.