You can specify a color range for a group using RGB, HSV, Lerp, or Gradients
If a color group has been assigned to a layer object, the color is applied after placement. More info
You can see preview colors in the bottom right corner if you move your mouse around.
Group mixing modes
You can choose from 4 options:
RGB: You can specify Red, Green, and Blue values within 0-255. You can choose from Fixed, Random, or Copy X/Y/Z like in the object layer's transformation settings.
HSV: You can specify Hue, Saturation, and Value values within 0-255. Otherwise this is the same as RGB Mode
Lerp: You can specify two separate colors, and the system gonna get a value between the two randomly
Gradient: You can specify a color gradient, and the system gonna get a color from it randomly