potassium permanganate, an oxidizer, might work on cypress. i've used it on oak, pine, and fir, to good affect.
mix with water, wear rubber gloves, brush on, wipe off if needed, or let it sit. the percentage of crystals to water will set its strength.
oak and fir can go a deep deep brown.
oak especially so, as the tannins react.
i've never taken anything to black.
every wood reacts differently.