All premodern cultures seem to have idealized white color and light skin just as white is the universal color of "purity" and legendary founders are described as light skinned.In every culture known, the ruling class has been made up of lighter skinned prople and rulers married their progeny to lighter skinned mates. When a darker skinned usurper founded a new dynasty he did the same thing. He married his sons and daughters to the lighter skinned eligibles. Aristocracies did/do the same. It is still the norm in all cultures though fading in the most advanced. It occurs among our own very "tolerant" and liberal elite.
I would discount the legends of founders or lawgivers or redeemers being light skinned just because their status as gods and heroes seems to require that characteristic because the founders and gods are "pure".