The Axis documentation you link to above is about Interop, the Axes Documentation is about VBA. The latter also has an Axis object, which has the properties and methods you want to apply. The documentation for that can be found from the link below the title
Represents a collection of all the Axis objects in the specified chart.
So, what you (probably) want is the documentation for the Axis object "Axis Object (PowerPoint)". In there you will find examples for the properties, e.g. the MajorGridlines
example goes like this:
With ActiveDocument.InlineShapes(1)
If .HasChart Then
With .Chart.Axes(xlValue)
If .HasMajorGridlines Then
' Set the color to blue.
.MajorGridlines.Border.ColorIndex = 5
End If
End With
End If
End With