HELMUT RUHEMANN'S INPAINTING TECHNIQUES
9 COLOR MATCHING IN OIL PAINTINGS
In choosing pigments to match a given color the overriding consideration is the degree of transparency required in each layer, covering for the ground, more translucent for the underpaint and design.
One should further keep in mind that old oil paint consists of two components: the oil medium which has to some degree gone brown through oxidation, and the pigments. Therefore, as a first step I base all colors (even black and white) on a mixture of red and green, covering or transparent according to the layer being inpainted. Then I add whichever pigments seem to match those of the painter's, again transparent or covering as required.
Here is a list of color matching tricks which I have found frequently useful:
For a deep inky black
Ivory Black with a little Prussian Blue.Skin tones
Light Red, (or Cadmium Red or Burnt Sienna) Viridian, Naples Yellow and Titanium White.Shadows
Add Ultramarine to medium tone.Skies
Viridian (not blue), Burnt Sienna and Titanium White.White garments, (shirts, ruffs, etc.)
Titanium White, Viridian, Burnt Sienna, and often some Ivory Black.Very dark hot glaze
Bone Black and Alizarin OrangeFiery red glazes on early Italian and Northern painting
Alizarin crimson, Alizarin Orange and Bone Black.Hot glazes, substitute for Alizarin Orange
Indian Yellow and Burnt Sienna.Brilliant, light colors
First underpaint in pure White, then glaze with transparent color.