Is brown hair more popular or is blonde or is brownish-blonde more popular?

It depends on what you mean by "popular". Do gentlemen prefer blondes? Yes, it seems most do, especially Caucasian men. Blonde hair whether natural or bleached, makes a woman seem younger, more innocent, softer and more approachable. In nature, Caucasian children are often born with a headful of coarse, dark hair which quickly falls out and is replaced by finer, lighter growth - hence, the term baby-fine. Other races tend toward more pigment and darker hair. After childhood, true, natural pale blondes are unusual. Certainly, they attract attention. Generally, all Caucasian hair darkens with age. Many women "touch up" their graying hair and blend it into a blonde shade to appear younger. Paler hair is more flattering to aging skin tones.