For the Gradient map type, you can set or modify the following parameters in the Parameters rollout:
Color #1-3: Sets the three colors that the gradient interpolates between. Click on them to display the Color Selector. You can drag and drop the colors from one swatch to another.
Maps: Click the select or create a map to display along with the color. Maps are blended into the gradient in the same way that the gradient colors are blended. You can add nested procedural gradients in each window to make 5, 7, 9-colored gradients or more.
Color 2 Position: Controls the center-point of the middle color. Ranges from 0 to 1. When it is 0, color 2 replaces color 3. When it is 1, color 2 replaces color 1.
Gradient Type: Linear interpolates the color based on the vertical position (V coordinate) while radial interpolates based on the distance from the center of the map (center is: U=0.5,V=0.5). Note that with both of these you can rotate the gradient using the angle parameter under Coordinates, which is animatable.
Noise Amount: When this is non-zero (ranges from 0-1) a noise effect is applied. This perturbs the color interpolation parameter using a 3D noise function based on U, V and Phase. For example, a given pixel is halfway between the first and second color (the interpolation parameter is 0.5). If noise is added, the interpolation parameter would be perturbed by some amount so that it may become less or more than 0.5.
Size: The scale of the noise function. Smaller values give smaller chunks of noise.
Phase: Controls the speed of the animation of the noise function. A 3D noise function is used for the noise, such that the first two parameters are U and V and the third is phase.
Regular: Generates plain noise. Basically the same as fractal noise with levels = 1. When the noise type is set to Regular, the levels spinner becomes disabled (because Regular is not a fractal function).
Fractal: Generates noise using a fractal algorithm. The Levels setting sets the number of iterations for the fractal noise.
Turbulence: Generates fractal noise with an absolute value function applied to it to make fault lines. This parameter can be animated continuously. Note that the noise amount must be greater than 0 to see any effects of turbulence.
Levels: Sets the number of fractal iterations or turbulence (as a continuous function).
When the noise value is above the Low threshold and below the High threshold, the dynamic range is stretched to fill 0-1. This makes for a smaller discontinuity at the threshold transition and thus produces less potential aliasing.
High: Sets the high threshold.
Low: Sets the low threshold.
Smooth: Helps make a smoother transition from the threshold value to the noise value. When smooth is 0 no smoothing is applied. When it is 1 the maximum amount of smoothing is applied.