I mean, they have light, Northern European-style skin, and Nordic-looking blonde hair. I honestly don't know how much whiter you can get.
I mean, this ultimately points to the fact that A Song of Ice and Fire/Game of Thrones are a work of fantasy, but from a metatexual perspective, it's pretty obvious that the Targaryens are coded as Nordic (hell, they even have an analogue to the Norman Conquest in Aegon the Conqueror, and the Normans were the descendants of the Nordics), the Dothraki are coded as a sort of mix of European stereotypes of "savage" Mongolians and Turks, the Mereeneese and Slavers Bay cultures are coded as pre-Islamic Middle Eastern, the Dornish and Braavosi are coded as a combination of Spaniards, Italians, and Greeks, the Wildlings are coded as Celts, and the Westerosi are coded as English.