Use warm undertone as a starting hypothesis, not a restriction
Golden blonde, caramel, chestnut, copper, and rose gold often echo warmth already present in the complexion, which can create an easy sense of harmony. That does not mean every warm shade works equally or that cool colors are forbidden. Depth and saturation can matter more: a very pale gold may wash out low contrast features, while a deeper ash brown can create clean definition even though its undertone is cooler.

