This example switches the background color on slide one in the active presentation between an explicit red-green-blue value and the color-scheme background color.
With ActivePresentation.Slides(1)
.FollowMasterBackground = False
With .Background.Fill.ForeColor
If .Type = msoColorTypeScheme Then
.RGB = RGB(0, 128, 128)
Else
.SchemeColor = ppBackground
End If
End With
End With