Is this some sort of soft-coded Grapheme-Color synethesia? I just found this remarkable optical illusion:



To do:
Fixate your gaze on the center of one of the figures and stare at it for some time (20-30 seconds) while it cycles (without moving your eyes). After several iterations you’ll start noticing that the empty outlines fill in with ghostly redish or bluish colors! These illusory colors are called “afterimages”. Interestingly, the colors of the afterimages vary, which is puzzling because they come from the same original figure. Moreover, the shape of the outlines determines the filled-in color, which is complementary to the color of the same shape in the original figure.

My question:

Is this some sort of soft-coded Grapheme-Color synethesia? 
Do people with Grapheme-Color synethesia have hard-coded afterimages in their brains?
Very cool image! As for your question, your link includes a link to the authors' poster, which allows you to "read more about the illusion and possible explanations."

From the poster:


  In conclusion, the observations so far suggest that the afterimage effect is not due to higher level effects of shape-specific coloured afterimages but rather to a rapid spreading of local patch-based afterimages within the outlines presented after the image.


From Wikipedia: "Like all forms of synesthesia, grapheme → color synesthesia is involuntary, consistent..." This illusion operates involuntarily as well, but is manipulable by the image designer, as the poster shows. Hence I think it's safe to say this has nothing to do with synesthesia as an abnormal condition, but it could probably be described in perceptual terms that apply to normative function. You might want to look for more of the authors' work or contact them if you're sufficiently curious! Please share with us here whatever info you receive if you do.