White is the lightest color and is achromatic (uncolored). It is the color of objects such as snow, chalk and milk and the opposite of black. White objects fully reflect and scatter all visible wavelengths of light. The white on television and computer screens is created by a mixture of red, blue and green light. The white color can be given with white pigments, especially titanium dioxide. In ancient Egypt and Rome, priestesses wore white as a symbol of purity, and Romans wore white robes as a symbol of citizenship. In the Middle Ages and Renaissance, a white unicorn symbolized chastity and a white lamb symbolized sacrifice and purity. It was the royal color of the kings of France and of the monarchist movement that opposed the Bolsheviks during the Russian Civil War (1917-1922). Greek and Roman temples were faced with white marble, and starting in the 18th century, with the advent of neoclassical architecture, white became the most common color for new churches, capitols, and other government buildings, particularly in the United States. It has also been used in 20th century modern architecture as a symbol of modernity and simplicity. According to surveys in Europe and the United States, white is most commonly associated with perfection, goodness, honesty, cleanliness, initiation, novelty, neutrality, and precision. White is an important color for almost every religion in the world. The Pope, head of the Roman Catholic Church, has been wearing white since 1566, a symbol of purity and sacrifice. In Islam and the Shinto religion of Japan, it is worn by pilgrims. In Western cultures and Japan, white is the most common color for wedding dresses and symbolizes purity and virginity. In many Asian cultures, white is also the color of mourning.