The reason they look [like] different colors is because our brain judges the color of an object by comparing it to surrounding colors. In this case, the stripes are not continuous as they appear at first glance. The orange stripes don’t go through the "blue" spiral, and the magenta ones don’t go through the "green" one.
If you don't believe it, see the closeup view at Bad Astronomy. Link - via j-walkblog
From the Upcoming ueue, submitted by Minnesotastan.
;)
http://tinyurl.com/mqk3xv
The two smaller squares are the same color.
Josef Albers was the man.