Regarding the two-toned hair: Even if Natalee's hair is natural (not dyed or even highlighted), it can easily be two-toned. When I was a teen I would pluck out a long blonde hair and find a totally different shade toward the scalp than the basically colorless shade at the ends.
Yaelle, you're right. A natural blonde will have many different shades (that's one way you can tell). My hair is blonde but towards the back I have strands of light brown and red. I'm just glad there's no gray yet!