color assimilation grid illusion

The image [..] is a visual/artistic experiment playing with simultanous contrast resulting from other experiments these days. An over-saturated colored grid overlayed on a  grayscale image causes the grayscale cells to be perceived as having color.
The processing needed to create the above image happened along with unrelated but significant code improvements In the last couple of weeks. I have been visiting mitch – a prolific GIMP contributors for collaboration – and lots of progress has been – and is still – being made on babl, GEGL and GIMP.

original article
See the effect in a video

You can now play with this effect and experiment for yourself. Get Gimp and enjoy!