redgreenblue  The box shows the color defined by the rgb bytes displayed to the left. Change the bits in those bytes and press enter, and the color of the box will update. You should see that changing the least significant bits (i.e. the right-most bits) in each byte has no discernible effect on the color. We know it changes, but by too little for us to perceive.
  
Backup from: http://www.usna.edu/CS/si110/lec/bl34/lec.html