Excel 2016: Changing the Colour of a shape to a non standard colour

Private Sub Worksheet_Change(ByVal Target As Range)
'Updateby Extendoffice 20160704
    If Intersect(Target, Range("A1")) Is Nothing Then Exit Sub
    If IsNumeric(Target.Value) Then
        If Target.Value < 100 Then
            ActiveSheet.Shapes("srRectangle1").Fill.ForeColor.RGB = vbRed
        ElseIf Target.Value >= 100 And Target.Value < 200 Then
            ActiveSheet.Shapes("srRectangle1").Fill.ForeColor.RGB = vbYellow
        Else
            ActiveSheet.Shapes("srRectangle1").Fill.ForeColor.RGB = vbGreen
        End If
    End If
End Sub

Hi All

I found the above code online which nearly suits my purpose, but I want to adapt the following line to something like

 ActiveSheet.Shapes("srRectangle1").Fill.ForeColor = RGB(255, 0, 0)

But this doesn't work, can anyone tell me how I can use any RGB code for the colour rather than just the stand vb colours?

Thx in advance!