Color: White

Kate Smith tells us that, "White aids mental clarity, encourages us to clear clutter or obstacles, evokes purification of thoughts or actions and enables fresh beginnings. It projects purity, cleanliness and neutrality.
"The appearance of white in a dream is thought to represent happiness at home." [sensationalcolor.com]
White is the absence of color if you are mixing paints,
but includes all colors if you are talking about light waves.