A Discussion on Color
by Mike Hanson

Reds
If I had to guess, I'd say that Ferrari Red has led to the most discussions about proper paint color. Ferrari red was a national color that over time became a corporate color. The 21st century Ferrari color for F1 cars is called “Rosso Scuderia,” and is also available as a production paint color. It's a bright red-orange that shows up very well on television and in print. In the 80's and 90's it was a darker red known as “Rosso Corsa.”
If you can't find or don't want to go to the trouble or expense of a custom mix, Charles Fox suggests you can get a good match using this technique:

The hot setup with Ferrari red in Tamiya is: (1) Tamiya white primer (over whatever primer you've used -- not polished to death, but left with a bit of "tooth", (2) Tamiya pink over that, again smoothed but not excessively, and finally (3) red. Smooth that reasonably, cover with clear, and polish that to your heart's content (so you're polishing clear and not color).

Classic Ferrari red is a very different matter. Moving into the 70's or earlier, Ferrari Red was just “red.” Any color that looked close was adequate. There are even stories of the Ferrari “works” team buying spray cans of red paint from Montgomery Ward's department store when racing at Daytona in the early 1970's.

Randy Enerson made this point about the classic Ferrari Reds:

On color - unless you have access to a time machine and bring a paint chip card with you, a Ferrari red would still be 'red'. It might be a little lighter or a little darker depending on the supply in the workshop at the time. But whether it is for covering the floor or the walls, it will make no difference at all on your model. The whole point of this discussion is rather pointless. Unless you paint a 'classic' Ferrari day-glo orange of course, no one could say that the color on your 'sharknose' or whatever doesn't exactly match Humbrol 19... No need to supercomplicate matters!

So, in general, any red that “looks right” would be correct for a classic Ferrari. The same would go for a classic Alfa Romeo or Maserati, though those marques tended to have darker reds, almost maroons.

Greens
When you refer to green in racing, the first color that will come to most folks' minds is British Racing Green (BRG). Interestingly, this is actually usually Jaguar Racing Green. It's a very dark non-metallic green. However, BRG does not necessarily have to be a dark green. It just has to be green. The international specification didn't indicate light, dark, metallic, or non-metallic.

Fielden Lundy put it this way:

British Racing Green has/had many hues. From the UDT/Laystall pale lime green, through the Lotus bright green to the BRM metallic blue/green to the Cooper dark blueish green.

I saw the team cars race in the late sixties, and they were definitely green. Dark, mind you, and with a lot of blue in the mix, but definitely green. If you look at a faithful color picture of the 59-60 factory Coopers when Brabham was driving, they were green. Or look at one of the restored cars running today.
Scott Truesdell has an interesting theory on where that “classic” BRG might have came from:
I have a theory about British Racing Green: I had decanted some of Tamiya's "Racing Green" spray to use with an airbrush. I have (or at one time had) a gross of 1 ounce scintillation jars into which I decant. So after setting on the shelf for a month or two, the BRG separated into a veritable rainbow of colors: 40% transparent blue, 30% dark gray/olive, 20% green, 10% iron oxide.

Surplus paint left over from WWII? Just mixed together and sold cheap?
If you're looking for a reasonable match for the classic BRG, check out Tamiya's TS-9 “British Green,” or order a bottle from Model Car World Paints.