The particle gradient mode.
This is used by MinMaxGradient to determine which mode to evaluate color gradients in.
| Color | Use a single color for the MinMaxGradient. |
| Gradient | Use a single color gradient for the MinMaxGradient. |
| TwoColors | Use a random value between 2 colors for the MinMaxGradient. |
| TwoGradients | Use a random value between 2 color gradients for the MinMaxGradient. |
| RandomColor | Define a list of colors in the MinMaxGradient, to be chosen from at random. |