The color agent is the physically or chemically definable and analysable pigment, the colorant.

The eye and mind achieve distinct perception through comparison and contrast. The value of a chromatic color may be defined by relation to an achromatic color - black, white or grey - or to one or more other chromatic colors.

Psycophysiological color reality is what I call color effect. Color agent and color effect coincide only in the case of harmonious polytones. In all other cases, the agency of color is transmuted into a new effect.

White square looks larger than the black square of the same size. White reaches out, black contracts (above). Same colors have different effects on different backgrounds (below).