by Mark L. Gottlieb (with a last-minute assist from Bridget Copley)

Solution: DORIS DUKE

Each picture was taken in a specific spot on one of the streets that radiates out from the Arc de Triomphe in Paris. (The Arc du Triomphe and its surrounding streets can be found here.) There are nine colors of ducks, each of which shows up in exactly two pictures. Take the ducks in light spectrum order (white first). For each color, trace the path from one pic to the other that goes through the Arc de Triomphe, and you'll get a letter in semaphore, spelling DORIS DUKE.

White - D

Pink - O

Red - R

Orange - I

Yellow - S

Green - D

Blue - U

Violet - K

Black - E

Missing link at "found here" restored in 2010 by archivists of Beginner's Luck