I know there is another thread about colour, i'm sure these two posts will correspond, but i thought i would post up my notes here too, there may be a few differences or even additions that may help =)
So when people say they use colour in ritual. They could mean the colour of their altar cloth, the colour of candles, your clothes while you perform the ritual, even colours of crystals sometimes too.
My old altar had a mirror infront of it, and sometimes i would use a certain colour to paint appropriate runes on the mirror. Colour holds alot of symbolism!!
So here are the colours i was trained in:
Black: Peace, Earth, silence, grounding. Black is all colours in the underworld, protection.
White: Pure spirit, stone. All colours in the upperworld.
Red: Birth, mind, blood, passion, desire. Ond travels on the breath. Power. (ond is 'life force', 'chi', 'prana' etc... its just another word for it)
Yellow: Fire, action, energy
Blue: Water, emotion, wisdom, self generated love
Violet: intellect, union of the God and Goddess, violet is blue and red in harmony.
Green: Sexuality, growth, harmony, fertility, strong heart emotion.
Pink: Flesh, sexuality, sexual love. Gentle heart emotion.
Brown: grounding, earth
Orange: fire in the head, vision, power, high psychic states.
As i said, people may have a different opinion about what colours mean... you just use what feels right to you because you are mostly where the power comes from.