Painting a Ship to Look Like another Ship
Experiments in Key West and Canal Zone Area with submerged submarines and airplane observers, described in Reference 3*, showed that black was practically the color of lowest visibility. A very dark blue, called "Pearl Harbor Blue," was found to be slightly less visible than black in Hawaiian waters, but the experiments were not sufficiently extensive to decide whether the slight difference was of essential importance. It turned out that the dark blue deteriorated and turned milky in a few weeks, whereas the black paint remained serviceable for several months. Therefore, black paint is specified in Measure 9. Improved formulas of Pearl Harbor Blue are being tested extensively in the Fleet at present.
Naval Research Laboratory Report H-1598, March 14, 1940, "Tests at Sea of February 1940, in the Key West Area of the Visibility of Submarines and Transparency Measurements of Navigable Waters."