TotalBoat Gleam 2.0 and TotalBoat Lust are oil-based varnishes, so, theoretically, any stains added to these products would have to be compatible with oil-based varnish. Keep in mind that stains that work great in their own proprietary systems, such as Minwax, are known to have poor results when added to TotalBoat varnishes. There are no specific stains that are recommended to be used with TotalBoat Lust or Gleam 2.0.
In general, a stain is most effective when it's applied directly to a particular substrate, such as wood, and intended to be overcoated with varnish. Stains are absorbed into the wood, accentuating the grain and changing the color of the wood. The problem with adding stain directly to varnish is that the stain dilutes the varnish and makes it more opaque, instead of clear. Opacity absorbs sunlight and degrades the varnish coating faster.