Hey guys,
Just thought you might like to give this a go

http://www.johnsadowski.com/big_spanish_castle.php#

I haven't quite figured out how it works yet buy maybe you'll have a clue. I presume it's something to do desensitisation of neurons in that area of the optic field or what not but whatever it is tis pretty cool
Anybody else have any good sites that I can procrastinate on (have several essays to write)?

Great find Savvylady, I think it works because the negative image gets left at the back of the eye when the othe image is shown and the 2 images merge to form the colour one pretty cool tho