...white-washed that way when Washington was raided in the War of 1812 and the whatever-colour-it-was house was scorched (Hence the term "whitewashing)
That's a myth. It's a common belief that during the rebuilding of the White House after the fire white paint was applied to it to mask the scorch marks, giving it its namesake hue.
However, the building was white to begin with, and was first dubbed "The White House" in 1811, three years before the British set it ablaze.