Optical Illusion showing how we see colours on differing backgrounds

This is a fun resource that simply shows how when we place objects on different coloured backgrounds, the background colour changes how we see the object that is in the foreground. I use it primarily to explain how colouring a black border around ideas makes them stand out from the page but this is also a bit of fun and tricks the children every time. They don't believe the 2 circles are actually the same colour. This is a PPT show which will start automatically and by clicking the mouse activates the animation. The same principal can be made using colour paper and circular disks.