The head belongs to a kouros, the standing male nude that defined Greek sculpture for generations - young, idealized, eternally poised between boyhood and manhood. But this one stands at a threshold of its own. Carved around 480 BC, it sits at the seam between the stiff, formulaic Archaic style and the new naturalism of the Severe style that would open the Classical age. The curling, ornamental hair still belongs to the older world. The face, calmer and more human, leans toward what comes next. It measures just 25 centimeters tall, a fragment of a figure otherwise lost, with only part of the pelvis surviving alongside it.

Run your eye over the curls and you may catch what remains of the yellow. That faded wash is why scholars named the piece the Blond Kouros, and it is far more than a curiosity. Greek marble statues were routinely painted in vivid colors - skin tones, dark eyes, patterned garments, hair in gold and red and brown. Weather, burial and centuries of cleaning stripped most of it away, leaving the white marble that later ages mistook for the original intent. The German researcher Vinzenz Brinkmann built much of his career reconstructing this lost polychromy, and copies of the Blond Kouros have been repainted to show how startling the original would have looked: a living, colored face, not a ghost in stone.

Whoever carved this head worked at the highest level of the craft, in the same Athenian world that would soon produce the greatest sculptors of antiquity. The piece has been attributed, tentatively, to one of the teachers of Phidias - the master who would later oversee the sculptures of the Parthenon. Hegias of Athens and Ageladas of Argos have both been proposed. The attribution can never be certain, but it places this fragment in extraordinary company, at the very root of the tradition that gave the world its idea of classical beauty.

The head was found in 1923, northeast of where the Acropolis Museum now stands, having lain buried in the sacred rock for nearly two and a half thousand years. Today it sits in that museum, a short walk from the spot where it was carved and broken. Visitors pass it easily, a small head among grander works. But linger, and the faint yellow in the hair becomes a window - proof that the marble world we imagine in silent white once blazed with color, and that this young man's curls were never meant to be pale at all.