Click the PDF to read the whole report.
Well, alrighty then. First let me state the anything put out by the California Energy Commission is immediately suspect. You need to consider their agenda and their tactics in evaluating anything they state as fact. These are the guys who at the time of this report wanted to ban dark colors on cars in California. These are the same people who have now successfully banned the sale of most automotive battery chargers that are transformer-based, forcing us to buy microprocessor-controlled high tech chargers at high prices, generally at low amperage resulting in longer charge times and no jumpstart capability in most new consumer chargers. Yet they state in one of their reports that the cost of charging batteries in CA will go down as a result of this mandate. I can get the citation if it is important to anyone.
Re the paint color analysis, I have seen this report in the past and it is flawed in many ways. First example is line 1 of the Executive Summary: "Air-conditioning in cars and small trucks lowers fuel economy by an estimated 22%." Well, sure, but the US DOE also states that driving at highway speed with your windows down uses more fuel than rolling up the windows and using the A/C. So a more accurate statement would be that hot weather lowers fuel economy by X%. You can turn on the A/C or you can roll down the windows. Choose your poison.
The researchers are overly excited about the real world effects of lighter colors vs darker colors. On page 6 of the report they state: "Use of cool-colored paint can reduce the soak temperature by a few degrees (3-5°F)." That is only soak temperature, and using my prior example, measured by me with my own digital thermometer on my own white truck parked in the sun in Ripley, with the cab interior at 185F, a 3F reduction would only be a difference of 1.6% in interior temp of a static vehicle, probably below what is known in psychology circles as JND (Just Noticeable Difference). It should also be noted that the authors of the report use Celsius when it suits their purposes and Fahrenheit when it suits other purposes. Up to this point on page 6, virtually all data was presented metric/Celsius, but when they wanted the reader to think there is a large impact to using light paint vs dark paint, they switch to Fahrenheit. Note that 3F difference between 185F and 188F is only about 1.7C. 3F seems like a bigger difference to most readers than 1.7C, so they went with Fahrenheit to shade the data without falsifying it.
See pages 8-9: "The roof of the black car was up to 25°C warmer than the silver surface. While soaking the cabin air temperature differences peaked around 5-6°C." Back to Celsius again, but 25C is about 45F, consistent with 4x4Junkie's 50F measured differential. However their cabin air temp delta of 5-6C stated here is inconsistent with the 3-5F delta stated on page 6. So, which is it? What you can take from this information is that there is a difference in sheet metal temps on dark cars vs light cars, and that translates into a difference in cabin air temps, but the difference in cabin air temps is relatively small compared to the difference in sheet metal temps.
See page 10/46: "Air conditioning has little effect on roof surface temperature, indicating that
the conductive heat
flow through the lined ceiling is small compared to the roof's solar heat gain." (Emphasis mine.) This supports my contention that, although white (or in this case silver) will be cooler than black, it really does not make that much difference in interior temperatures. See also page 19/46, Table 2: "thermal emittance, 0.83 (black), 0.79 (silver)." Not a heck of a lot of difference in the emittance between light and dark roofs, is there?
So, getting back to the OP's question: Sure you can paint the roof of your blue Suburban white. It will help a little, but don't expect a huge improvement.