How about a reverse color illusion? In the image by Prof. Kitaoka, you can see two distinct shades of green, one dark and one almost day-glo, but in fact the same color is used for both ``green" spirals.

In this amazing image by Prof. David Novick, relying on the same ``color assimilation illusion," all the spheres are precisely the same color, despite appearances!

Again, all the spheres have the same base color, as you can verify by using the color picker on an image editor.  This general type of illusion is usually referred to as the Munker Illusion.  There is not much on the internet about the form of the illusion seen here, with horizontal or vertical grid lines of various colors.  The illusion can also be used to color a black and white photo, just by superimposing grid lines of the appropriate color.  The illusion still works if the photo is reduced in size so that the grid is almost invisible.