I doubt it could be proved. I have read before that she had light brown hair and also that it was blonde.
Thanks yarddog.... :)
Light brown hair used to be called "dirty blonde" and, later (I think), "American blonde." Israelis sometimes specify blondini zahav (golden blonde) as opposed to just blondini, which I gather covers more of a range of color. So your two sources may agree on the color, just not on the terminology!