Gradient plots are colored based on a color gradient. Users can define custom color gradients in a plot by opening the "Plot -> Manage color gradients" dialog.

In this dialog, the color gradients of the current FCX document are listed. Gradients can be added and removed - and of course, their color pattern can be defined. At least two colors - the starting and the end color - need to be defined. Up to 7 colors (#1 - #7) can be defined for a gradient. The gradient will then be formed by spanning each color in order. A preview of the gradient can be seen under "Gradient".
Hint: to remove a color from the gradient, perform a popup-trigger mouse click on it (this is usually the right mouse click).