if you are looking for a triangle, check the shape's Node count (triangles have 4 Node.Count)
Sub addColorhexagon_1()
Dim oPres As Presentation
Dim oShape As Shape
Dim oSlide As Slide
Dim j As Long
Dim r As Long
Dim g As Long
Dim b As Long
Set oPres = ActivePresentation
For Each oSlide In oPres.Slides
    For Each oShape In oSlide.Shapes
        If oShape.Nodes.Count = 4 Then
            oShape.Fill.ForeColor.RGB = RGB(50, 50, 50)
        End If
    Next
    Exit For
Next
End Sub