We may never know who the Mona Lisa was or what she’s smiling about, but we do have some idea of how Leonardo da Vinci created the sombre mood and smoky colors that add to her allure.
Leonardo would first create a detailed underpainting in a neutral gray or brown, then apply his colors in transparent glazes on top. Some of the underpainting would show through the layers, subtly helping to create form. On his palette were muted, earthy browns, greens, and blues within a narrow tonal range. This helped give a sense of unity to the elements in the painting. No intense colors or contrasts for him, so no bright red for Mona’s lips nor blue for her eyes (though it doesn't explain why she hasn't got eyebrows!).
Soft, gentle lighting was crucial to his paintings: “You should make your portrait at the hour of the fall of the evening when it is cloudy or misty, for the light then is perfect.” Facial features were not strongly defined or outlined, but conveyed by soft, blended variations in tone and color. The further from the focus point of the painting, the darker and more monochromatic the shadows become.
Leonardo’s technique of softening colors and edges with dark glazes is known as sfumato, from the Italian fumo, meaning smoke. It’s as if all the edges have been obscured by a haze of transparent shadows, or smoke. Creating colors by applying glazes gives a painting a depth you cannot get by applying a color mixed on a palette. Or in his own words: “When a transparent color lies over another color differing from it, a compound color is composed which differs from each of the simple colors”.
For a modern version of Leonardo’s palette, select a small range of transparent earthy colors whose midtones are similar, plus black and white. Some manufacturers produce a range of neutral grays ideal for a tonal underpainting.