...old b/w film depicted dark yellows and oranges as dark grey or black, and blue as a lighter shade of grey...look closely: you'll notice the globes are reversed too...
...you see it all of the time on old Gulf station photos - in the photo, the orange is darker than the blue in the letters...
...for the same reasons, 'non-photo blue' pencils and Amberlith and Rubylith were once used to create mechanical art for photographic reproduction...the pencils because they wouldn't reproduce in the final artwork; and the Amber and Rubylith, because they would...
http://en.wikipedia.org/wiki/Rubylithhttp://en.wikipedia.org/wiki/Non-photo_blue_pencil