Use: To change the color,style,etc of all lines (shapes) on active sheet

Sub format_all_lines_using_vba()
Dim shp As Shape

For Each shp In ActiveSheet.Shapes
If shp.Type = msoLine Then ' choose shape
shp.Line.Weight = 2 ' adjust width
shp.Line.ForeColor.RGB = RGB(255, 0, 18) ' choose color
shp.Line.DashStyle = msoLineDashDot ' choose dash style to apply
End If
Next

End Sub