Not all stains are compatible with marine wood finish systems such as Sikkens Cetol Marine. It is recommended that Cetol Marine be applied directly to bare wood, or to a previously applied Cetol Marine finish that's in good condition, and not to stain or wood finishes other than Cetol Marine. All varieties of Sikkens Cetol Marine (except Gloss) have their own color, so tinting is not necessary—nor is it recommended.
As an added note, Cetol Marine Gloss is not recommended as a stand-alone product, and should only be used over one of the other Cetol Marine finishes.