Lines on white background);the bleeding into the gray background is strongest for the middle luminance lines(red);the bleeding into the black background is strongest for the darkest lines(purple). The colors are cinstained by the illusory border formed by the luminance change in the radial lines.( An illusory border is a border that is perceived where one does not exist.lates,a border linking the luminance discontinuities that exist only along the redial lines.)Thus blending of colors is strongest when colors are close to the same luminance and can be perceived as being part of the same surface. The colors bleed until they hit the illusory border,consistent with the idea that object borders constrain the spreading of the Color system.
A similar kind of color spreading can be seen in many impressionist paintings. Blending of individual strokes of color within an area of approximately equiluminant colors is seen in various regions in Monet's The Palazzo Ducale as seen from San Giorgio Maggiore. Each surface consists of many colors of paint that blend even though they are left unmixed on the canvas. The blending occurs within each region,with each region defined by the average luminance of the brushstrokes,as shown by the luminance version on the right.