I have stripped the varnish off below decks and like the pale colour of the wood. Is there an oil or wax that I can use that will not darken the colour?
As it is down below and out of the weather, I'd think strongly along the lines of white shellac. This is much paler than normal common-or-garden shellac. Unfortunately you won't be able to use this in any places that get rough treatment, like a table-top, but for locker doors, roof beams and the like, it should be fine. You may find it harder to get than normal shellac, but a decent cabinetmaker should be able to tell you where to find an industrial supplier Your Yellow Pages phone directory may also be useful.
Peter.