Three colours are esp. important for sacral purposes in antiquity; they are white, black, and red, the last being understood in the widest sense, to include purple, crimson, even violet.
White is in general a festal colour, associated with things of good omen, such as sacrifices to the celestial gods (white victims are regular for this purpose in both Greece and Rome). See e.g. Homer's Iliad 3. 103, where a white lamb is brought for sacrifice to Helios; as the Sun is bright and male, a white male lamb is brought for him, while Earth, being dark and female, gets a black ewe‐lamb. It is the colour of the clothing (see dress) generally worn on happy occasions. In Rome, white horses drew the chariot of a triumphātor.
Black on the contrary is associated with the chthonian gods and mourning, and with the dead. These facts explain why ‘white’ and ‘black’ respectively mean ‘lucky’ and ‘unlucky’ when used of a day, etc. (See race.) The natural association of white with light and black with darkness is explanation enough, but note also that white garments are conspicuously clean, black ones suggest the unwashed condition of a mourner; see dead, disposal of.
Red might suggest blood, and therefore death and the Underworld, but also blood as the source or container of life, and also the ruddy colour of healthy flesh and various organs of the body. Perhaps because red, or purple (stress falling on sheen), is the colour of light, red is on occasion protective, e.g. the praetexta (see toga) of Roman magistrates and children. But it is also associated with the burning heat of summer.
Subjects: Classical Studies.