Selecione o intervalo e execute esta macro:
Sub Main
Dim oCurrentSelection As Variant
Dim oRows As Variant
Const nCellBackColor = 15132415 REM # "Blue gray"
Dim i As Long
oCurrentSelection = ThisComponent.getCurrentSelection()
If oCurrentSelection.supportsService("com.sun.star.table.CellRange") Then
oRows = oCurrentSelection.getRows()
For i = 0 To oRows.getCount()-1 Step 2
oRows.getByIndex(i).setPropertyValue("CellBackColor", nCellBackColor)
Next i
EndIf
End Sub