No. It's not an illusion.

This is an image I made from using the Gimp to auto-white balance each disc in the image to show that in fact the color of the middle squares would be the color you mistakenly identify them as. Green and orange. Here is the original.
In fact there is a lot of incorrect usage of terms in these illusions. Especially the forms section. The examples talk about the lengths and angles of the objects pictures. But the are talking specifically about the image's lengths and angles. Cheers