The Place of White in the Color Spectrum
White is the color of milk and fresh snow, the color produced by the combination of all the colors of the visible spectrum.  As a symbol, white is the opposite of black, and often represents light in contrast with darkness. According to surveys in Europe and the United States, white is the color most often associated with innocence, perfection, the good, honesty, cleanliness, the beginning, the new, neutrality, lightness, and exactitude. The word white continues Old English hwīt, which ultimately from a word in Common Germanic *χwītaz also reflected in OHG (h)wîz, ON hvítr, Goth. ƕeits. The root of the word “white” is ultimately from Proto-Indo-European language *kwid-, surviving also in Sanskrit śveta “to be white or bright” and Slavonic světŭ “light”. The Icelandic word for white, hvítur, is directly derived from the Old Norse form of the word hvítr. Common Germanic also had the word *blankaz(“white, bright, blinding”), borrowed into Late Latin as *blancus, which provided the source for Romance words for “white” (Catalan, Occitan and French blanc, Spanish blanco, Italian bianco, Galician-Portuguese branco, etc.). The antonym of white is black. White is the color the human eye sees when it senses light which contains all the wavelengths of the visible spectrum.  This light stimulates all three types of color sensitive cone cells in the eye in nearly equal amounts.  Materials that do not emit light themselves appear white if their surfaces reflect back most of the light that strikes them. Before Isaac Newton, most scientists believed that white was the fundamental color of light. Newton demonstrated that this was not true by passing white light through a prism, breaking it up into its composite colors, and then using a second prism to reassemble them. White light can be generated by the sun, by stars, or by earthbound sources such as fluorescent lamps and white LEDs. Incandescent bulbs do not produce white light; their light leans toward the long-wavelength color red. On the screen of a color television or computer, white is produced by mixing the primary colors of light: red, green and blue (RGB) at full intensity, a process called additive mixing (see image below). White can be made by a variety of other combinations of colored light, thanks to a process called metamerism.
The Symbolism of White in Mythology and Folklore
White was one of the first colors used by paleolithic artists; they used lime white, made from ground calcite or chalk, sometimes as a background, sometimes as a highlight, along with charcoal and red and yellow ochre in their vivid cave paintings.  In ancient Egypt, white was connected with the goddess Isis. The priests and priestesses of Isis dressed only in white linen, and it was used to wrap mummies.  In Greece and other ancient civilizations, white was often associated with mother’s milk. In Greek mythology, the god Zeus was nourished at the breast of the nymph Amalthea. In the Talmud, milk was one of four sacred substances, along with wine, honey, and the rose.  The ancient Greeks saw the world in terms of darkness and light, so white was a fundamental color. According to Pliny the Elder in his Natural History, Apelles (4th century BC) and the other famous painters of ancient Greece used only four colors in their paintings; white, red, yellow and black; For painting, the Greeks used lead white, made by a long and laborious process. A plain white toga, known as a toga virilis, was worn for ceremonial occasions by all Roman citizens over the age of 14-18. Magistrates and certain priests wore a toga praetexta, with a broad purple stripe. In the time of the Emperor Augustus, no Roman man was allowed to appear in the Roman forum without a toga. The ancient Romans had two words for white; albus, a plain white, (the source of the word albino); and candidus, a brighter white. A man who wanted public office in Rome wore a white toga brightened with chalk, called a toga candida, the origin of the word candidate. The Latin word candere meant to shine, to be bright. It was the origin of the words candleand candid.In ancient Rome, the priestesses of the goddess Vesta dressed in white linen robes, a white palla or shawl, and a white veil. They protected the sacred fire and the penates of Rome. White symbolized their purity, loyalty, and chastity. 
Tree of Life Attribution
The color attributed to Kether is white.  In the King scale of color “brillance represents the colorless luminosity of Kether.”  In the Queen scale, Kether “being previously unconditioned brillance, is now articulate as white.”  In the empress scale, croley tell us that “White flecked gold. The white is a reflection of the white brillance of Kether; but the gold is an ornament, and thus indicates the mystery of the Holy Guardian Angel, who finds added perfection when invoked by his client, the gold of Tiphareth.”  This is a concrete example of the power behind these Qabalistic symbols, for the colour is also a Kether colour – as for instance in the title. The Wite Head; white contains all the other colours as kether contain all the subsequent manifestations. (Gareth Knight, A Practical Guide of Qabalistic Symbolism, p. 69) The colour assigned to the Atziluth of kether is brillance, which transcends all colours, as Kether transcends all creation. (Gareth Knight, A Practical Guide of Qabalistic Symbolism, p. 71)
 Israel Regardie, A Garden of Pomegrenates, p. 40; Aleister Crowley, 777, p. 7.
 Aleister Crowley, 777, p. 67.
 Aleister Crowley, 777, p. 71.
 Aleister Crowley, 777, p. 74.
 Shorter Oxford English Dictionary, 5th Edition (2002). “of the colour of fresh milk or snow.” See also Webster’s New World Dictionary of American English, Third College Edition, (1988): “Having the color of pure snow or milk.” See also The Random House College Dictionary of the English Language, Revised Edition,(1980): “of the color of pure snow; of the margins of this page, etc.” Shorter Oxford English Dictionary, Oxford University Press, 5th Edition (2002) See also Petit Larousse (2005): “de la couleur de la neige, du lait. Lumiere resultant de la combinaison de toutes les couleurs du spectre solaire.” (of the color of snow, of milk. Light resulting from the combination of all the colors of the solar spectrum.)
 Eva Heller (2000), Psychologie de la Couleur- Effets et Symboliques, pg. 130–146
 Of the color of radiated, transmitted, or reflected light containing all the visible rays of the spectrum.” Webster’s New World Dictionary of American English, College Edition.
 Wyszecki & Stiles. Color Science (Second ed.). p. 506
 Michel Pastoureau (2005), Le Petit Livre des Couleurs, p. 47
 Anne Varichon (2000), Couleurs- Pigments et Teintures dans les Mains des Peuples, pg. 16 .
 John Gage (1993) Color and Culture. P. 29.
 Anne Varichon (2000), Couleurs- Pigments et Teintures dans les Mains des Peuples, pg. 16