This example adds a rectangle to myDocument
and then sets the foreground color, background color, and gradient for the rectangle's fill.
Set myDocument = ActivePresentation.Slides(1)
With myDocument.Shapes _
.AddShape(msoShapeRectangle, 90, 90, 90, 50).Fill
.ForeColor.RGB = RGB(128, 0, 0)
.BackColor.RGB = RGB(170, 170, 170)
.TwoColorGradient msoGradientHorizontal, 1
End With