Change the font on all slides

I join lots of powerpoints together to make one large one and I like all the writing to be the same font, size and colour. There is a button in Home to replace all of one font with another:

But this will not change the colour and size, and requires me to change each font individually. So I use the following macro:

Sub ArialFont()
Dim sld As Slide
Dim shp As Shape

For Each sld In ActivePresentation.Slides
    For Each shp In sld.Shapes
    If shp.HasTextFrame Then
    If shp.TextFrame.HasText Then
        With shp.TextFrame.TextRange.Font
            .Size = 24
            .Name = "Arial"
            .Bold = False
            .Color.RGB = RGB(0, 0, 0)
        End With
    End If
    End If
    Next shp
Next sld
  
End Sub

In the macro I can easily change the font, colour and size to apply to the whole powerpoint.