As per the title.
Simply this:
Green tea regenerates more stamina the farther your slider is towards Nature, and Black Tea regenerates more stamina the farther your slider is towards Industry.
Base slider would be 75% of current regen from both types, with 5% added or subtracted based on the slider.
Full Nature would restore 100% of current regen from green tea, 50% current regen from black tea, and the reverse if you are full Industry.
(Or 100% at base, and 125% for going with the specialization and 75% for going against. Things to think about.)