The 6,981st B 17 was the last B17 that was built at Boeing Seattle, each of the colored items on the plane, are construction paper cut into the shape of a bomb, showing every target that B 17s had bombed in WW2

 https://www.facebook.com/photo/?fbid=527365027117631&set=a.126528027201335

You can see video of the roll out of this last B 17 at https://secure.boeingimages.com/archive/Rollout-of-Final-Boeing-Seattle-Built-B-17-Flying-Fortress-2JRSXLJWH62O.html on April 9th 1945