I apologize if this is a RIDICULOUS question:

[Robhu]

Dark colors absorb heat. And I don't think there is any t-stat to tell them when to stop absorbing heat.
Light colors reflect heat.
In high temp areas even most houses have light colored roofs for that reason.
And people with campers use that aluminum colored stuff instead of tar to recoat camper roofs. People have a tendency to wear light colored clothes.
Black cars are beautiful when clean. But in a hot dusty area it is very hard to keep them looking good.
White or light colored cars are much more forgiving when it comes to keeping them looking sharp.
No matter what color car you buy one of those cardboard thingys that fits inside the w/shield to block the suns rays is a good idea. (Not to be used while driving, LOL) Glass magnifies the suns heat even more than dark colors.
No I don't live in Arizona, but I've been in Texas and Oklahoma where it can get pretty hot and had a black car.

[keninaz]

I have had 3 black cars in my life, all when I was younger. They are very nice looking when they are kept very very clean.
The problem of course is keeping them clean.
Any scratch, dent or any other imperfections show worse than any other color as will an improper repair job.
Been there and done that.
Any dark color is hard to keep clean but black is the worst.

[sickofIL]

Dark colors absorb heat. And I don't think there is any t-stat to tell them when to stop absorbing heat.
Light colors reflect heat.

There is a t-stat of sort and it is basic thermal dynamics as to how it works. But first a little about color.

There are 3 types of light that could be used as a heat source, ultraviolet light; infrared light and visible light. Ultraviolet and infrared light both have an effect but mostly the heat comes from visible light. There is a measure of reflective value for visible light that is called "Light Reflective Value." (LRV) This is what is important here. Based on LRV white reflects about 80% of visible light and black reflects about 5% of visible light.

Now, the basic structure of the exterior of a typical car is metal and glass. The metal is painted so the metal is a conductor and the paint is the absorber. So paint color does effect how fast the metal heats. However, given the same heat source, the sun, there is the same amount of heat applied to each color so eventually both black and white cars surfaces will become the same temperature. For one to get hotter you would need an additional heat source. So as far as the metal surfaces the difference is time.

Next you have the glass which would be the same on both cars. (unless it is tinted on one and not the other) The glass does not intensify the heat but allows the heat to pass through. (unless your windows are ground into magnifying glasses) What makes the interior of the car so hot is the fact that it is a closed space. Without constant air flow the temperature continues to climb but again only to a certain temperature which is based on the heat source, the sun. This is why it doesn't get as hot when you leave the windows open. A good example is when it is cold in winter. (not Tucson) After your car sits in the sun for awhile the interior becomes warm even though it is cold outside in the cold.

Now for the t-sat part. This is just basic thermal dynamics. Given the same amount of heat (BTU's) all objects will come to equalibrium at the same temperature given the same materials and size. Color only will change time.

Take the insulation in house. Additional insulation value will slow the rate of heat loss or gain but no amount of insulation will stop heat loss or gain. Eventually the inside of identical houses with different insulation will become the same temperature if you turn off the a/c or heat.