the Mercedes W25 race car entered in the 1934 changed colors to become race eligible for weight

in 1934, this Silver Arrow was the winner without paint.

The race organizers were working to reduce the vehicles’ power and with it their racing speed, as tires and brakes weren't evolving as fast as the top speed and aerodynamics, so they limited engine size at first... this car was a 205 cu in, and weighed 750 Kg, at 354 Hp then it was upgraded in steps that went:
M25A 3360cc 354HP,
M25AB 3710cc 398HP,
M25B 3990cc 430HP,
M25C 4300cc 462HP
ME25 4740cc 494HP

the 750-kg formula had been created to curb the ever-escalating speed of the powerful racing cars – built for example by Alfa Romeo, Bugatti and Maserati.

The very opposite was achieved since design engineers at once resorted to bigger displacements.

The actual output of the eight-cylinder engine at the beginning amounted to a massive 354 hp (260 kW). Several engine versions with boosted power output followed. The M 25 AB (3710 cc) variant generated 398 hp (293 kW), followed by the M 25 B (3980 cc and 430 hp/316 kW) and C (4300 cc and 462 hp/340 kW) variants, and eventually, in 1936, the ME 25 version (4740 cc) producing 494 hp (363 kW) – always at 5800 rpm.

With the W 25, the Mercedes-Benz engineers ended up removing the previously customary white paint to make weight, because the car was 1 kilogram too heavy.

Until the paint was sanded off. Paint was leaded back then... and heavy.

https://www.mercedes-benz.com/en/mercedes-benz/classic/history/mercedes-benz-silver-arrows/
https://www.supercars.net/blog/1934-mercedes-benz-w25/

Neubauer told how these white-painted W25s then proved overweight during scrutineering for the next race, the EifelRennen at the Nürburgring in June.

 Another non-start was unacceptable; in Berlin, a former house painter was expecting a return on his government's investment.  (Hitler who was bankrolling the Mercedes team for winning results to support his German superior race propaganda)

What to do? Neubauer had a brainwave: "Scrape off the paint!" Next morning, in bare metal, the new cars met the 750kg limit and works driver Manfred von Brauchitsch won the race. "And so silver replaced white as the German national racing colour - the Silver Arrows had been born."

http://www.telegraph.co.uk/motoring/motorsport/2749203/The-history-of-the-Silver-Arrows.html

Initial power ratings for the car was 314 bhp at 5,800 rpm. Using a new fuel mixture provided by Standard Oil that replaced the gasoline/benzol with methyl alcohol horsepower was bumped to 354 bhp. A new era of exotic racing fuels was evolving

http://www.grandprixhistory.org/merc25.htm

Adopting a national official racing color goes back about 117 years, to the Gordon Bennett races

Motor racing's first prescribed list of national colours had emerged for the 1900 Gordon Bennett Cup race. They've changed a bit since then.

 In 1900 just four national colours were allocated: blue for France, yellow for Belgium, black for Germany, red for the United States.

How did the British get the color green?
There are two stories, equally plausible:

A)  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..."

B)  Road and Track magazine reader Hayden R. Shepley's comment, concerning an article in the Cyril Posthumus in April 1969... The origin of the color British Racing Green is 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 after Parliament had a special act passed to allow this. This act allowed certain public roads to be closed, thereby making this the first ever closed circuit race in automobile history. As a compliment to the Irish, all the English cars were painted a dark green.

I haven't read yet how Germany went from Black to White, but they went from White to Silver right there with the 1934 W25.

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.

http://justacarguy.blogspot.com/2011/07/trivia-why-red-is-italys-racing-color.html
http://justacarguy.blogspot.com/2006/11/british-racing-green.html

as for why there are now Grand Prix races, and no Gordon Bennett Cup races?

The Gordon Bennett was contested between teams of no more than three cars, representing each nation's motor industry. The French felt this to be enormously unfair, as their motor industry was by far the world's largest and most diverse,  and yet they were restricted to the same number of race cars 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.

the oldest vehicle repair shop in the USA? Probably. The Fitzpatrick Brothers in Dorchester/Boston Massachusetts still located on the same spot since 1894

Founded in 1894 by Thomas and Martin Fitzpatrick.

In 1919, and in 1929 their sons joined, and then the grandsons Harry and Frank, began in 1954 and 1956 respectively. Finally, greatgrandson  Neale began working full time for the company in the late 1980s.

They transitioned from a horse-drawn wagon repair shop working long hours and instead of body techs they had blacksmiths, wheelwrights and carpenters back then, to a technically advanced collision repair center in 1926, when they became the first auto body repair shop to use spray guns, and they stopped using a paint brush. They are now Mon - Fri, 630am to 330pm

When they celebrated the business' 100th year on September 8, 1994, the Fitzpatricks mailed over 1,000 thank-you cards to all the names accumulated in their database, which was only 6 years old, no one had thought to keep track of the customers for the first 100 years.

To put some perspective on how long Fitzpatrick Brothers has been in business, in 1894 the sport of basketball was only three years old, Dwight Eisenhower was four, the camera was six, the Statue of Liberty was eight, Einstein was 15, and Grover Cleveland was president then.

How did they survive the great depression?  From 1931 to 1937, that generation of Fitzpatricks stayed afloat through a community bartering effort. Cash was almost non-existent, weekly salaries averaged $5, and if you could sweep the floor for a quarter you were doing pretty well for yourself. If they needed groceries, they repaired the grocer's truck. Need some hardware supplies? Surely the store owner was in need of a paint job. When the electrician needed some work done on his car, he'd offer to rewire your building.

It wasn't until the '50s that the business would see its most significant transformation since gasoline. No longer would insurance companies simply acknowledge a claim and send a check. They wanted to see the work now. "The business became really tough," said Franny. "Insurance companies began insisting on negotiating. You had to deal with an agent and present him with your bill. And those were days when $200 and $300 jobs were major operations."

In order to streamline their appraisal and billing process, they purchased a $4,500 computer from Radio Shack in 1979

What made a difference, the brothers say, is that nobody in the family was ever mandated to work for the family business. Harry and Franny's father and uncle never asked them to give up their accounting and radio engineering degrees respectively. They chose the family business like their father and his brother. Harry's two sons, Neale and Scott, have continued the tradition. "It's funny how things work out," Franny philosophized. "We have always had two Fitzpatrick brothers running the business with two more stepping in. We have all wanted to be a part of this. In this day and age when families are falling apart, it's nice to see this kind of longevity."

“It wouldn’t have worked the same way anywhere else, we’re probably the only body shop in the whole world surrounded by residential houses,” Fitzpatrick said. “And 90 percent of those houses are out customers, even when someone gets married and moves to Milton or Quincy, they tell their kids to come by the shop to get work done.”

Fitzpatrick said that while he appreciates his business’ history, his real pride comes from what lays ahead.  “It’s a funny thing, but we’ve been here now for more than 100 years. You won’t become a millionaire doing this kind of work, but it’s satisfying knowing you’re doing the same work as your father, as your grandfather. You know it’s the work you can keep on doing.”

http://www.fitzpatrickbrothers.com/about-us.html
http://www.fitzpatrickbrothers.com/article.html
http://www.autobodynews.com/index.php/northeastern/item/11201-oldest-shop-on-the-east-coast-keeps-family-legacy-alive.html
http://www.dotnews.com/2011/hailing-dot-s-stalwarts-they-built-businesses-and-they-stayed
hat tip to Repaint Reporter v75.2, the PPG company magazine

You know how companies like bars seem to have a tradition of framing the first dollar earned for good luck? Don't you wish this company had an 1894 dollar of some type, bank note, silver dollar, whatever... framed? I think that would be awesome, don't you?

History has some completely astonishing stories that we never have heard of. Rarely does it intersect with this auto hobby, and the coachbuilders, but

The book, the Kellner Affair tells the fascinating story of how some people in the French luxury car business who fought bravely against the Nazi occupation force in Paris.

Because you've never heard about Mont Valérien, the prison fortress and Nazi place of execution.

One early morning, the condemned had been transported to the place of execution. The firing squad made ready. The famous coachbuilder Jacques Kellner and Georges Paulin, the gifted designer of gorgeous aerodynamic cars, were dead.

For the Gestapo-controlled court that had handed down the death sentences and the German conscripts who fired the bullets, it was a case of finishing the business, once the culprits had been caught and “justice” metered out. Some names to cross off a list. For France and the nascent French Résistance, it was the loss of heroes who had been willing to give their lives to fight the Nazis and paid the price. For their relatives and loved ones, it was the unbearable loss of what they held dearest in the world.

The author had this to say:

"We started out wanting to tell the story of Joseph Figoni’s life and the story of the marvelous designs he created – that will be a large work: Joseph Figoni, le Grand Couturier de la Carrosserie Automobile (the book is in English). It will be published simultaneously with The Kellner Affair. But as with our previous book about Jacques Saoutchik, we also wanted to set that story into relief against the backdrop of important events that transpired in the protagonist’s lifetime. Since Joseph Figoni became involved—albeit peripherally—with the Phill reseau that counted his colleague and competitor Jacques Kellner and the designer Georges Paulin among its members, much of this backdrop necessarily concerned the fall of France in 1940, the subsequent occupation by the Germans, the formation of the resistance group and what happened to it. First we were going to write it into the body text of the Figoni book. We soon realized that was no good, so we decided to write about Kellner, Paulin and Phill as a series of interludes inserted in the Figoni biography – sort of like a novel with two parallel storylines, and structured in such a manner that they could be read independently. Then the number of interludes started growing. Every time a new dossier came our way, it was clear that the hunt could not stop until we were reasonably sure there were no more to be found. With the dossiers that will be reproduced in an appendix in the back of this book, it became clear that the parallel storyline route also would not work. So we have decided to bite the bullet, and The Kellner Affair will now be a stand-alone book. The Kellner Affair will both be included as a fourth volume with the Figoni book, and published on its own."

 Peter M. Larsen and Ben Erickson