I am working on some decking made of old scaffold boards. A colour I want is in Manns water based stain for internal use. I will be staining the bare wood after cleaning then covering with Barrettine Wood Preserve and two coats of decking oil. I have already used water based food colouring covered with the same oil preserve and finish so would this be a problem. As it is oil over water I thought I might be OK but....can anyone confirm this ?