Yellow ochre and red ochre are two of the oldest pigments known to man.

YELLOW OCHRE

Color:   Yellow ochre is an earth pigment that contains hydrated iron oxide.  Much of it is found in Roussillon, France.  Otherwise, mostly in parts of Italy.   It’s a cool, greenish-yellow and varies to orange, slightly.

Opacity:  Opaque

Uses:  Yellow ochre is a common color found on a decorative painter’s palette.  It is a very pleasing color for wall glazes.  When mixed with other colors like ultramarine blue and raw umber, yellow ochre is used with other colors to create tonalities in faux marble.  Because of its opacity, it does not work well with woodgraining (use RS – Raw Sienna instead).  

RED OCHRE

Color: Red ochre is an earth pigment that contains hydrated iron oxide.  When you burn yellow ochre in an oven, it becomes red, creating a red ochre.  Much of the variance of color comes by how hot/long the burn is as well as where the yellow ochre is from.

Opacity:  Very opaque

Uses:  Red ochre is often mixed with glazes for a variety of decorative finishes.  It is commonly used to create tonalities in faux marble.  Because of its opacity, it does not work well with woodgraining (use raw sienna instead).   **Red ochre is very strong and can overtake a color quite quickly.  Along with Prussian blue, red ochre is the most potent color.   That is why you’ll see snap lines made with red ochre chalk ― because it a strong color.