Ochre Ground
Ochre is an iron oxide clay, and one of the very oldest colouring materials in use anywhere. Its range runs from a pale straw yellow through gold to a deep red-brown, depending on the iron content and on whether the raw earth has been heated. Heating drives off water and shifts the colour toward red, which is the difference between a yellow ochre and a burnt one.
Used across a whole wall, ochre behaves like light rather than like colour. A room with an ochre ground will look sunlit on a grey day, which is why the colour has such a long history in northern interiors as well as in Mediterranean ones. The effect is strongest when the tone is slightly greyed; a clean, saturated yellow gives glare rather than warmth.
The colour has an awkward relationship with artificial light. Under warm lamps an ochre ground can slide toward orange and take the rest of the room with it. Where the room is used mostly after dark it is worth choosing a duller, more earth-bound ochre than looks right in daylight, and letting the lamps do the warming.
Ochre grounds carry almost any pattern. They were the standard field for stencilled borders and hand-blocked papers for a long period, precisely because they make a printed colour look printed rather than pasted on.