When you know the right color but it looks wrong

I am a classic car collector. Our club has found a photo of one of the first Cadillac cars ever made. They only made this car in three colors - maroon, red, black.

When I use the colour picker, to get the right color, I can't seem to achieve a realistic color (unless the car was actually black, yet the black seats and black radiator are so much lighter than the body in the photo).

Where am I going wrong, please?? Should I intensify, or lessen the RGB....??

We desperately want to know what the car's real color was (the greyscale photo is far right). Is there a way you experts can assist, please?

Thanks

Pete