Gradient Editor Using Hermetian Splines:
Click and drag any of the gray control points to modify the spline.
Click outside of a control point to create a new control point.
Press Q/A to increase/decrease the red derivative at the highlighted point.
Press W/S to increase/decrease the green derivative at the highlighted point.
Press E/D to increase/decrease the blue derivative at the highlighted point.
Press R to delete the highlighted point.

Red/Green	Green/Blue	Blue/Red