property Item.BackColor2 as Color
Specifies the color at the ending boundary line of the gradient item's caption.

TypeDescription
Color A color expression that indicates the color at the ending boundary line of the gradient item's caption.

Use the BackColor2 property to specify the second background color when painting its background in gradient. Use the BackColor and ForeColor properties to specify the item's background and foreground colors. Use the BackColorList property to specify the default background color for the group's list. Use the BackColor property to specify the control's background color.

In VB.NET or C# you require the following functions until the .NET framework will provide:

You can use the following VB.NET function:
     Shared Function ToUInt32(ByVal c As Color) As UInt32
         Dim i As Long
	 i = c.R
	 i = i + 256 * c.G
	 i = i + 256 * 256 * c.B
	 ToUInt32 = Convert.ToUInt32(i)
     End Function 
You can use the following C# function:
private UInt32 ToUInt32(Color c)
{
	long i;
	i = c.R;
	i = i + 256 * c.G;
	i = i + 256 * 256 * c.B;
	return Convert.ToUInt32(i);
}