I too find it strange how NASA selects which images they colorize and which pictures are shown.
This image shows the Mars Exploration Rover Spirit´s "hand," or the tip of the instrument deployment device, poised in front of the rock nicknamed Adirondack. In preparation for grinding into Adirondack, Spirit cleaned off a portion of the rock´s surface with a stainless steel brush located on its rock abrasion tool, seen here at the top of its hand. The image was taken by the rover´s panoramic camera.
u can clearly see the flag on all of those pics, f00