The studies I have seen (long ago)  suggested that yellow on black was better than black on yellow, white on black better than black on white, and red on black better than black on red.

However, there are so many confounding factors that one should not take a simplistic view of the matter. It depends on the resolution, illumination, hue, saturation and sources of visual noise.

It emphatically is not a matter that you can settle without a good helping of common sense in any particular application.

Slightly off at a tangent. ...

An interesting study a few years ago concluded, surprisingly, that red cars are the most difficult to see in the distance. I'm not sure if it is true in all light conditions, but when on a journey, test it for yourself. I guess it's because the red car reflects about the same amount of light as the road surface, while other colours create more contrast.

It all depends on the time of day, and driving conditions. At night, when it is dark, from a distance, the letters and numbers almost 'merge' into one another, because your eyes are seeing dark all around and it can be hard to focus on white letters from far away. However, if it was a white background (in the same conditions) there would be something for the black letters to show up more clearly against.

However, most studies have confirmed that yellow on black or visa versa are much easier to read than black on white.