Apple Color 1.0 - Manual (Page 230)

230 Chapter 10 Secondaries
Important: Curves cannot be animated with keyframes, although just about every
other parameter in the Secondaries room can be.
These curves work much differently than the curves controls of the Primary In room.
Each of the secondary curve controls defaults to a flat horizontal line running halfway
through the graph area.
The visible spectrum is represented along the surface of the curve by a wrap-around
gradient, the ends of which wrap around to the other side of the curve. The control
points at the left and right of this curve are linked, so that moving one moves the
other, to ensure a smooth transition if you make any adjustments to the red.
Adding points to the surface of this curve lets you define regions of hue that you want
to adjust. Raising the curve in these regions increases the value of the particular aspect
of color that’s modified by a specific curve, while lowering the curve decreases the value.