Color spirits - wraithlike tints.
One color, the barest amount to achieve a hue that is subtle, almost not there, yet still visually registers. The palest possibility for that one color. Color homeopathy!
This is the polar opposite of the Raven Clan. Whereas the Ravens are saturated shades, the Spirits are tints. A tint is the addition of white to any color to make paler hues. They are dilutions of a full strength mix and this is where they seem homeopathic to me. Color taken all the way to its essence.