A flat color placed between two parents reads as their mixture when it is a believable middle-ground in hue and lightness

When a third color C is placed spatially between two “parent” colors A and B, C can be made to read as the optical mixture of A and B — the eye interprets the arrangement as though A and B blend where C sits. The condition is that C be a believable middle-ground of A and B in BOTH hue and lightness (the “middle mixture”): too far toward either parent and the illusion collapses. Because C convincingly reads as a blend, it also tends to lose apparent opacity and look like an overlap/transparence — the coupled consequence of the same middle-mixture calibration. This is the mechanism behind opaque transparency studies (see the cover-study principle). It applies to any flat medium: paper, paint, or digital fills.

Examples

Blue and Yellow with their middle green arranged in overlapping rectangles: the green area reads as the blue-yellow blend and, consequently, as a transparent overlap. In p5.js: three flat rectangles in an overlapping T with a correctly calibrated middle color read as a mixed/glass region.

Assessment

Select two colors A and B and find the middle mixture C that reads convincingly as their blend when placed between them. Then shift C’s lightness toward A and describe how and why the mixture reading breaks down.