Adobe ( /əˈdoʊbi/, UK /əˈdoʊb/; Arabic: الطوب) is a natural building material made from sand, clay, water, and some kind of fibrous or organic material (sticks, straw, and/or manure), which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for some of the oldest existing buildings in the world. In hot climates, compared with wooden buildings, adobe buildings offer significant advantages due to their greater thermal mass, but they are known to be particularly susceptible to earthquake damage.

Buildings made of sun-dried earth are common in West Asia, North Africa, West Africa,South America, southwestern North America, Spain (usually in the Mudéjar style), Eastern Europe and East Anglia, particularly Norfolk, known as 'clay lump. Adobe had been in use by indigenous peoples of the Americas in the Southwestern United States, Mesoamerica, and the Andean region of South America for several thousand years, although often substantial amounts of stone are used in the walls of Pueblo buildings. (Also, the Pueblo people built their adobe structures with handfuls or basketfuls of adobe, until the Spanish introduced them to the making of bricks.) Adobe brickmaking was used in Spain strating by the Late Bronze Age and Iron Age, from the eighth century B.C. on. Its wide use can be attributed to its simplicity of design and make, and the economy of creating it.

Color or colour (see spelling differences) is the visual perceptual property corresponding in humans to the categories called red, green, blue, and others. Color derives from the spectrum of light (distribution of light power versus wavelength) interacting in the eye with the spectral sensitivities of the light receptors. Color categories and physical specifications of color are also associated with objects, materials, light sources, etc., based on their physical properties such as light absorption, reflection, or emission spectra. By defining a color space, colors can be identified numerically by their coordinates.

Because perception of color stems from the varying spectral sensitivity of different types of cone cells in the retina to different parts of the spectrum, colors may be defined and quantified by the degree to which they stimulate these cells. These physical or physiological quantifications of color, however, do not fully explain the psychophysical perception of color appearance.