The 25 June 1914 issue of The Automobile provides this interesting tidbit in an article regarding the 1915 International 500 Mile Sweepstakes race:

Racing colors in the next Indianapolis 500-mile race, it is announced, will be uniform, according to the nation which a car represents. German machine will thus be white; French, blue; English, green; Belgian, yellow; Italian, red; and American, white and red. This move will do away the freakish individual color combinations which in the past have marred speedway racing, and at the same time give bolder relief to the international aspect of the sport. Credit for the idea is due E.C. Patterson, the wealthy Chicago sportsman.

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