With the Urban Heat Island Effect and the thermal inefficiency of black roofs well documented, it has always surprised me that heat reflective roof paints have not been mandated on new house builds and dark roof colours banned.
Several years ago, students at the Massachusetts Institute of Technology developed phase-change polymer gel-filled roof tiles dubbed Thermeleon tiles that changed colour from light during hot sunny days to dark during cold periods. While commercialisation is yet to happen, this forum's more environmentally aware new home builders should be interested in the technology discussed in the link below.
https://phys.org/news/2009-10-color-cha ... inter.html
EDITED March 1 2018. Swapped links.
This was a very exciting development but there has been no updates for several years now.