Studies have shown that students have been more willing to take this rice purity test than to take a very private STD test because they felt the purity test results were more of a no judgement zone.
Russians come from a plethora of different people, but Slavs are the most common. Slavs traditionally have light brown or even blond hair, with only a smaller part of them endowed with dark hair from southern ethnicities, like so: Black hair color is actually pretty common, especially the further you go East.
Another very common interpretation is the association of  colours with the main parts of the Russian Empire: white thus  represents Belarus (White Russia), blue Ukraine (or  Malorossia, Little Russia), and red Great Russia.