Colors in dreams represent energy, emotions, and viberations. First consider what that single color in your dream means to you and your own personal associations and relationship with that color.

Red indicates good news, passion, anger. It can also be a warning to control your temper.
Blue indicates enlightenment, insight and relief from worry; assistance from outside sources.
Green means peace, tranquility, the Earth, money, a journey or good news.
Yellow in dreams can indicate intellect, a problem or puzzle to be solved, possible setbacks.
Pink in dreams can represent love, compassion, the attainment of a dream.
Purple: Spirituality; status in one's own circle. Increased social life, or the desire for same.
Orange: Message from a great Master. Metaphysical or spiritual knowledge.
Brown: Illness. Materialism.
Black: Unhappiness. A rough road ahead. Something that the dreamer needs to know. In extreme cases, a death, but the dreamer's death is never shown.
White: Purity. Success well earned.
Gray is a rather depressing color; some mystics believe it to be the color of the aura of a prison. Some sources believe it to indicate a slow period in the dreamer’s life, when he or she is merely “marking time.”
A swirl of color: Great joy, happiness, success. Dreams attained. Luck in love.