Application.ActiveWindow.Page.Shapes.ItemFromID(XXX).CellsSRC(visSectionObject, visRowFill, visFillPattern).FormulaU = "1"

Option Explicit
Sub FormatShapes()
    Dim oApp As Object
    Dim doc As Object
    Dim shp As Shape
    Dim pg As Page
    Dim i As Integer

    Dim cGreen As String
    Dim cGrey As String
    Dim cBlue As String
    Dim cRed As String

    cGreen = "THEMEGUARD(RGB(51,204,51))"
    cGrey = "THEMEGUARD(RGB(191,191,191))"
    cBlue = "THEMEGUARD(RGB(117,159,204))"
    cRed = "THEMEGUARD(RGB(197,90,17))"

    Set oApp = GetObject(, "visio.application")
    Set doc = oApp.ActiveDocument

    i = 1
    For Each pg In doc.Pages
    Application.ActiveWindow.ViewFit = visFitPage
        For Each shp In pg.Shapes

            If Not shp.OneD Then
                If shp.Name Like "Rectangle.*" Then
                    With pg.Shapes.ItemFromID(shp.ID)
                        Debug.Print pg.Name & " _ " & shp.Name & " - " & .CellsSRC(visSectionObject, visRowFill, visFillPattern).FormulaU

                        'change fill color from pattern to solid ?
                        If .CellsSRC(visSectionObject, visRowFill, visFillPattern).FormulaU = "2" Then  '1 - solid, 2 - pattern
                            .CellsSRC(visSectionObject, visRowFill, visFillForegnd).FormulaForceU = cGreen
                            .CellsSRC(visSectionObject, visRowFill, visFillBkgnd).FormulaForceU = cGreen
                            .CellsSRC(visSectionObject, visRowFill, visFillPattern).FormulaU = "1"
                        End If
                    End With
                End If
            End If

        Next shp
        i = i + 1
    Next
End Sub