graphic from http://www.petrolicious.com/the-colorful-history-of-national-racing-hues-an-introduction-1-of-4
An interesting little story: Prince Scipione’s Itala, painted bright red for the race, fell into the harbour when it was being unloaded for the big event! To prevent rust, the car was repainted battleship grey…the only paint the harbour-workers had on hand at the time. If you’ve ever wondered why Italian race-cars are red today, it’s because after the Prince won the race all the way back in 1907, Italy adopted red as its official racing-colour and red remains that color to this day.
This reminded me of the reason why green is the official racing color or British carshttp://justacarguy.blogspot.com/2006/11/british-racing-green.html
from 1903 when the British wouldn't allow the Gordon Bennett race to be held in Britain. Ireland was asked to hold the race on their roads, as a compliment to the Irish, all the English cars were painted a dark green.
Doung Nye wrote a good piece in 2005, with a different reason for the British cars green color, here is a part of it:
For decades, French racing cars were classically blue, German became silver, the Japanese were allocated white, and Italian racers wore red. At Montreal and Indianapolis, and in this country for the Goodwood Festival of Speed next weekend, the Renault campaigned by World Championship leader Fernando Alonso will be a pale blue flash, the challenging McLaren-Mercedes as driven by Kimi Raikonnen a streak of predominant silver, Jenson Button's re-emergent BAR-Honda is white, and the factory Ferraris will blaze by in fiery red.
The long years of national racing colours, with no overt advertising, crumbled in 1968 after motorsport's previous big-money backers - the international oil companies - slashed support. Non-motoring sponsors had to be found and the rule makers dropped opposition to on-car advertising. Colin Chapman immediately sold space on his Lotus cars to John Player for its Gold Leaf cigarette brand. Almost overnight, modern Grand Prix cars became mobile advertising hoardings.
Motor racing's first prescribed list of national colours had emerged for the 1900 Gordon Bennett Cup race. It was to be contested between teams of no more than three cars, representing each nation's motor industry.
This was outrageously unfair to the French, whose motor industry was by far the world's largest and most diverse, yet they were restricted to the same number as little Belgium... or emergent America. French discomfort led eventually to their replacing the Gordon Bennett Cup from 1906 with their own new race - the Grand Prix. Any manufacturer could race there, against the best.
In 1900 just four national colours were allocated: blue for France, yellow for Belgium, black for Germany, red for the United States. In 1901 the great capital-to-capital Paris-Berlin race saw wealthy British sportsman Charles Jarrott order a Panhard. The car was painted green... M. Clément gave me a reason for this. My number in the race was 13, because no one else would have it. But they had been struck with the happy idea of painting the car green (the French lucky colour) to nullify the unlucky number..."
The following year saw Jarrott's friend Selwyn Edge's Napier win the Gordon Bennett Cup for Britain. Napier had adopted green as its favoured livery, and between them British Racing Green became enshrined as this country's national racing colour.
French fortunes had collapsed under first the German racing colossus, then the Italians and British. After 1957 there were no French Grand Prix cars - until 40 years ago, in 1965, a young motorcyclist named Jean-Pierre Beltoise won the year's most important Formula 3 race, at Reims, driving a slender vehicle from a new French manufacturer, an offshoot of Matra aerospace. French blue Matra cars carried Jackie Stewart to his first World Championship in 1969, and later Graham Hill to Le Mans 24-Hours victory too.