Ochre is a natural earth pigment containing hydrated iron oxide, which ranges in color from yellow to deep orange or brown. It is also the name of the colors produced by this pigment, especially a light brownish-yellow. A variant of ochre containing a large amount of hematite, or dehydrated iron oxide, has a reddish tint known as "red ochre".

Ochre is a family of earth pigments, which includes yellow ochre, red ochre, purple ochre, sienna, and umber. The major ingredient of all the ochres is iron (III) oxide-hydroxide, known as limonite, which gives them a yellow color.

• Yellow ochre, FeO(OH)•nH₂O, is a hydrated iron hydroxide (limonite) also called gold ochre
• Red ochre, Fe₂O₃, takes its reddish color from the mineral hematite, which is an anhydrous iron oxide.
• Purple ochre, is identical to red ochre chemically but of a different hue caused by different light diffraction properties associated with a greater average particle size.
• Brown ochre, also FeO(OH), (goethite), is a partly hydrated iron oxide.
• Sienna contains both limonite and a small amount of manganese oxide (less than five percent), which makes it darker than ochre.
• Umber pigments contain a larger proportion of manganese (five to twenty percent) which make them a dark brown.

When natural sienna and umber pigments are heated, they are dehydrated and some of the limonite is transformed into hematite, giving them more reddish colors, called burnt sienna and burnt umber.

Ochres are non-toxic, and can be used to make an oil paint that dries quickly and covers surfaces thoroughly.

Raw yellow ochre	Ground yellow ochre pigment

Yellow ochre:

How it is made: Coloured earth is mined, ground and washed, leaving a mixture of minerals--essentially rust-stained clay. Ochre can be used raw (yellowish), or roasted for a deeper (brown-red) colour from loss of water of hydration.

Chemical Properties: An ochre contains manganese oxide and iron hydroxide, Fe₂O₃ • MnO₂. In acids it dissolves in part leaving a yellow solution; hydrochloric acid gives it an odor of chlorine. In alkalis it discolours a little and when heated, becomes a reddish brown. It has the same properties as natural umber. Ochre is one of many earth-tones created by natural iron hydroxide. When heated, it turns red, losing its chemically bound water content to become thick and dense. Under moderate heat, yellowish-red colours are produced. However, the stronger the heat the more rich and saturated the colour produced, which if mixed with white create colder tones than one would expect. The colouring agent is of an iron oxide. To heat, the ochres have to be pure and free from adulterant admixtures such as chalk, because this would create quick-lime if heated.