Site was temporarily unavailable when I tried to post a comment, so here it goes:

This post clears up a few misconceptions for me, thanks for that.

I think you will enjoy the following link about "context" related illusions: http://www.psy.ritsumei.ac.jp/~akitaoka/color12e.html

Akiyoshi Kitaoka is a university professor from Japan that has created a very extensive and amazing collection of illusions, documenting so many subtle ways our eyes play tricks on us.

His homepage is really worth exploring:

http://www.psy.ritsumei.ac.jp/~akitaoka/index-e.html