What msoFillMixed fill format type stands for in PowerPoint context ?
If there are two or more shapes in a shaperange, they may have different fill
properties. In that case, PowerPoint returns msoFillMixed:
Create two shapes, give them the same fill, select them both then run this.
Then try it after you change the fill type for one of the shapes:
With ActiveWindow.Selection.ShapeRange
If .Fill.Type = msoFillMixed Then
MsgBox "Now you see what it's for"
Else
MsgBox "Sorry. Keep trying ..."
End If
End With