Can you use a stain on wood under spar varnish?
Michael Dresdner: Yes, of course, but if it is an exterior application, choose a 100% pigment based stain, since dyes will fade in sunlight.
Greg Williams: Most stains, dye or pigment type, can be used under spar varnish. The most important caution with regard to a pigmented stain is to avoid applying too thick or heavy a coat of stain without properly wiping it off before brushing on the varnish, and to avoid over brushing the varnish. If there is only a small amount of binder in the stain, over brushing the varnish may dissolve that binder and move the stain.