Bottom line is it doesn't matter. Chrome wrapping even a white car will make it cooler.
Thermodynamics and Reflective Insulation | Energy-Efficient Houses
Reflectivity + Emmisivity =1
Why would you sacrifice reflectivity to gain emmisivity?
Chrome is 97% reflective
White is 90% reflective
Reflecting maximum energy will always win.
Chrome: out of 100W of IR energy 3W gets through
White: out of 100W of IR energy 10W gets through
Of the 3W that gets past our chrome surface 3% gets dissipated or 0.09W
Of the 10W that gets through the white surface 10% gets dissipated or 0.1W
Leaving us with a net heat gain of 2.91W for Chrome vs 9.9W for White.
The emmisivity of white would need to be three time greater to match the performance of chrome, because it's simply admitting too much heat in the first place.
And that's before we get to the fact that low-E means the A/C is more effective once on the move.
Must be a reason why construction uses silver foil and not white.
I'm not exactly re-inventing the wheel.
Chrome or white are both good choices, chrome happens to out perform white and I think better suits the appearance of modern cars.