When depicting groups of people or animals, the Egyptians usually alternated the colour on them, to give a sense of perspective. Hence the colour will often alternate between two shades, light then dark, in pictures of groupings.

The main colours used by the Egyptians were:

Black
Black (kem) was the colour of night, and of death. Black symbolised the underworld, but could also symbolise resurrection, life and fertility. In this respect black was interchangeable symbolically with green. This association probably comes from the fertile black silt of the Nile, deposited in its annual flooding and ensuring the fertility of the land. Egypt itself was known as the black land (kemet). Black was also interchanged with blue for representing the night sky.

Black was associated with funerary deities such as Anubis and Osiris, interchangeably with green in the latter case. In the later Macedonian and Ptolemaic periods black stones were used almost exclusively for magical healing statues. Carbon from soot, charcoal or burnt animal bones was used to produce black.

Blue
Blue (irtiu or khesbedj) was used to represent both the heavens and the waters. Both these symbolisms are those of life and rebirth, the eternal sky and the annual flooding of the Nile, which recalled the primal flood of myths. Blue was also associated with fertility, as the power of the fecundating Nile river, so vital for the crops the ancient Egyptians depended on. As well as being interchangeable with black for the heavens, blue was also interchanged with black as an underworld colour.

Blue was associated with Amun-Ra, and sometimes with Osiris. Ptah, Horus, Khnum, Re-Horakhty and Nuit were all often depicted with blue bodies. The Eye of Horus amulets were most often blue, symbolising their heavenly power. The blue pigment was formed by combining iron and copper oxides with silica and calcium.

Green
Green (wadj) was the colour of growth and of life itself, a life-positive colour seen in the plants that sustained the culture through food, medicine and writing (the papyrus). To do green things was a term used to describe good deeds.

In some early texts the afterlife is referred to as the Field of malachite, and green came to be associated with resurrection through the annual return of the green plants. Osiris as Lord of the Underworld was usually depicted with green skin, and Hathor was also associated with this colour. Copper oxide or malachite was used to make the colour green for artwork.

Red
Red (desher) was seen as the colour of blood and fire, and could symbolise life and regeneration. Red also represented the forces of chaos, and dangerous powers outside of man's control. Red was specifically associated with Set, as was red hair. Red also represented the untamed vastness of the desert, and sometimes foreign lands as dangerous places.

Red ink was used to write the hieroglyph for evil, and for the demon or unlucky days. To do red things was to perform evil acts. However, red was also used to depict Re, and the fierce radiance of the sun. Red was used to colour the Eye of Re serpent amulet. The red colour was created by using oxidized iron and red ochre.

White
White (hedj or shesep) was the colour of cleanliness, associated with sacredness and ritual purity. Clothing, especially that of the priesthood, was usually shown as white. This is well illustrated by the Instructions of Merikare, where the term wearing white sandals is used to describe being a priest. Many of the sacred objects were made from white alabaster, and many of the sacred animals were also white, such as oxen, cows and hippopotami.

White was also used interchangeably to describe silver, which was sacred to the Moon. The crown of Upper Egypt was known as the White crown, and white was the heraldic colour of southern Egypt. The god Nefertem, whose symbol was the white lotus flower, often had his statues made of silver, to illustrate his link with the colour white. Chalk and gypsum were both used to give a strong white colour.

Yellow
Yellow (khenet or kenit) and gold were the colours of the sun, and symbolised eternity and constancy. The ancient Egyptians believed the flesh and bones of the gods were made of gold, and so it was a natural progression to see yellow and gold as sacred colours, and to use gold in the construction of statues of the deities. The Egyptians had several sources of yellow, ochre and imported orpiment (arsenic trisulphide) being the most commonly used.

Other Colours
Brown, grey, orange and pink were also sometimes used, but as only secondary colours. Such colours were formed by adding white or black to the primary colours, or mixing them accordingly.

( Extract from the book - "Heka - The Practices of Ancient Egyptian Ritual & Magic by David Rankine - for more information on this book click here)