This area shows GIMP's basic palette, consisting of two colors, the Foreground and Background, used for painting, filling, and many other operations. Clicking on either of the color displays brings up a Color Editor dialog, which permits you to change it.

Clicking on this small symbol resets the Foreground and Background colors to black and white, respectively.

Clicking on the small curved line with two arrowheads causes the Foreground and Background colors to be swapped. Pressing the x key has the same effect.