Line Color: The color of the line around the perimeter of the shape. If no line color is defined, no line will be drawn around the perimeter of the shape.
Background color: The color to use for unselected shapes
Selection color: The color to use for selected shapes
Selection color gradient: The color to use to create a gradient of color when the shape is selected. In the gradient, the selection color gradient defines the color at the top left corner of the shape. The Selection color (see above) defined the color at the bottom right corner of the shape.
Red Selection color gradient and blue Selection color: