property Calendar.Background(Part as BackgroundPartEnum) as Color
Returns or sets a value that indicates the background color for parts in the control.

TypeDescription
Part as BackgroundPartEnum A BackgroundPartEnum expression that indicates a part in the control
Color A Color expression that indicates the background color for a specified part. The last 7 bits in the high significant byte of the color to indicates the identifier of the skin being used. Use the Add method to add new skins to the control. If you need to remove the skin appearance from a part of the control you need to reset the last 7 bits in the high significant byte of the color being applied to the background's part.
The Background property specifies a background color or a visual appearance for specific parts in the control. If the Background property is 0, the control draws the part as default. Use the Add method to add new skins to the control. Use the Remove method to remove a specific skin from the control.

The following VB sample changes the visual appearance for the header of months. The sample uses the "" skin. 

With Calendar1
    With .VisualAppearance
        .Add &H24, "D:\Temp\ExCalendar.Help\green.ebn"
    End With
    .Background(exDateHeader) = &H24000000
End With

The following C++ sample changes the visual appearance for the header of months:

m_calendar.GetVisualAppearance().Add( 0x24, COleVariant("D:\\Temp\\ExCalendar.Help\\green.ebn"));
m_calendar.SetBackground( 8 /*exDateHeader*/, 0x24000000 );

The following VB.NET sample changes the visual appearance for the header of months:

With AxCalendar1
    With .VisualAppearance
        .Add(&H24, "D:\Temp\ExCalendar.Help\green.ebn")
    End With
    .set_Background(EXCALENDARLib.BackgroundPartEnum.exDateHeader, &H24000000)
End With

The following C# sample changes the visual appearance for the header of months:

axCalendar1.VisualAppearance.Add(0x24, "D:\\Temp\\ExCalendar.Help\\green.ebn");
axCalendar1.set_Background(EXCALENDARLib.BackgroundPartEnum.exDateHeader, 0x24000000);

The following VFP sample changes the visual appearance for the header of months:

With thisform.Calendar1
    With .VisualAppearance
        .Add(36, "D:\Temp\ExCalendar.Help\green.ebn")
    EndWith
    .Background(8) = 603979776 	&& exDateHeader
EndWith

where the 603979776 is 0x24000000 in hexa, and 36 is 0x24 in hexa