As the car is a very good deal, and I'd rather not paint it, is this a safety concern? Just trying to figure how much offsetting color I need, if any for safety. Thanks. I understand the risk of not getting timed because of visual issues.
I photograph cars at speed from near the 3 mile mark most every year, and can attest to the fact that some cars are almost impossible to see in certain lighting conditions. That last part is the key,
car visibility changes dramatically during the day depending on the relative direction of the sun to the car and your point of view. There are several cars that I have a devil of a time getting pictures of, because the autofocus on the modern digital camera cannot figure out where the car stops and the salt starts. Sometimes I get beautiful sharp pictures of the dirt embankment and the line of cars on the short course behind the car, but the car in the foreground is out of focus because the camera decided it was not the object of the photo. As a result all the pictures are just a bit out of focus, and sometimes the camera gets so confused, it zooms the lens completely out of focus trying to find the object I am trying to take a picture of.
(same applies to the completely black cars!!! )
If you want good pictures of your car at speed (when there is very little time for the photographer to get focus) do not paint the car completely black completely white or use contrasting color bands around the numbers except black drop shadow or white drop shadow depending on the number color. A white number with a red band around the perimeter on a black car looks like a fuzzy edged number to the camera at 1000' ft and 200 mph. The same number size in white or yellow on black will look tack sharp to the camera (and the eye) at distance.
The silver cars with dark numbers absolutely light up when the sun is on the viewers side, if the lighting is on the other side and it is a hazy day or early in the morning they are very hard to pickup as they appear light gray at distance and just blend into the background.
My suggestion is to use a contrasting color band at least 6 and preferably 8 inches wide or wider. Since the rocker panels are typically darker in most lighting conditions, put the stripe low on the door (which will help the lights pickup the car) or a strong color band that wraps over the car side to side similar to the Hot Rod Camaro.
Remember that the actual rocker panel will get covered with salt during a run, so a dark band will give little color contrast if placed too low on the door/rocker area after you make a run. Low mid door below the bodies belt line would be best.
(by belt line I mean the point on the body where the slant of the body changes from slanting toward the top of the car vs slanting toward the ground. The area above that line will always appear lighter and the area below that will naturally appear darker)
A black plastic air dam (if rules allowed in your class) will solve the timing issue.
The cars that are the easiest to photograph (ie see) are the cars that have large areas of contrasting color, and large numbers. By contrasting color I mean both the color difference and the brightness difference. Pale yellow on white is a color contrast but has very little brightness contrast which is the thing your eyes first pickup on distant objects. You see things by finding edges, then your brain assembles a shape that fits the edges.
If you can cover the digits of your cars numbers with your hand, I probably won't even bother trying to get a picture of your car, especially if the number color is of similar gray tone to the background color (ie red on black, green on gray or brown etc.)
I have lots of pictures of motor cycles that I have no clue who they belong to, because their numbers are so small and poorly placed (high on the rear fender right where the sun glare shows up), that I cannot identify the bike in the image. In many cases the only distinctive feature on the black bikes is the color of the helmet and the driving suit (assuming they are not wearing black leathers too). In some cases even with a long telephoto shot, I cannot read the bike number (and some car numbers) even after blowing up the image in post processing. There are several cars with 2 inch high lettering in red on a dark background that I never could figure out what the car number was until I got a shot of them on the return road.
In almost every case, the issue is numbers (digits) the size of a playing card or smaller, and low contrast colors.
One of the worst offenders being dark red on black, or dark blue/purple on black, or blue on red where both colors are of similar gray tone.
If you want something easy to read, never use dark blue or purple on red, The human eye cannot focus both colors at the same time, and in extreme cases of purple on red the numbers seem to float above the background because of the need of the eye to shift focus back and forth between the lettering color and the back ground color.
Dark red on black, may be easy to read in good light when you are 20 ft away, but is impossible to even see when photographed at 1000' in low contrast lighting.
Your sponsors will also appreciate it if lettering on the car is readable in pictures that might only be 2 inches across in a magazine or web page.
/end rant about color number choices car/bike owners use
Cheapest solution would be to buy a roll of 2" wide blue painters masking tape and use it to put some contrasting color stripes on the body.
It will peel off after your runs with no problem but is dark enough and a bright enough color that it will show up at a distance.
Larry