Using color damages a Sister's realm. The damage is smaller per point if the color is poisonous to her, and bigger per point if it is a favored color. The implications for farming are clear: infuse trees with poisonous color to mitigate realm damage.
What about combat? Aside from realm damage, is the power of the colors affected as well? Do ten points of a favored color have the same amount of attack power as ten points of a nature-friendly, poisonous color? Does the duration of golems or other glyphs depend on color type as well as the amount used?