If I look at the picture without focusing (i.e. thereby seeing it as 2D), A and B look the same color.

If I look at the picture and focus but cover the green cylinder with my hand, they can look either the same or different (depending on whether or not I notice the shadow in that case.)

I agree with Andy Woods: this is no illusion at all, except in the sense that it is an "illusion" that the board is three dimensional.