I got my hands on some older sample disks recently and set them out in the sun to see which were the hottest and coolest. Lacking a surface probe, I used the back of my hand to feel the relative temperature. They were laid out on a reasonably insulated (wood) surface. To eliminate any bias, I shuffled them and ranked them blindfolded, moving the coolest to the left and the hottest to the right.
To my surprise, yellow was coolest. So I flipped the disks and repeated the operation -- got the same result. Next I got another set (different thicknesses, same colors) and did it again. The result, from coolest to hottest in both sets?
The second set felt a little different but somehow came out in the same order.
Looking closely, the overall colors are actually a blend of component colors. Dune had brown specks whereas Papaya had white. Maybe that accounted for the temperature difference. Regardless, here's a subjective analysis:
--Papaya and Dune were close and coolest, but the difference was noticeable.
--Hibiscus and Caribbean were also close in temperature and formed a distinctly warmer group.
--Moss was easily the hottest -- no trouble picking it out.
Total range in temperature distinct but not huge -- maybe 15 to 20 degrees F+/-???
Colors change slightly from year to year so there could be some variations. But this gives a good idea of what to expect if hull temperature is a factor in your color selection.