With talking to Gray, i put this little list here. Information may be changed in the future, please note any contradictions or mistakes.
Green Herb: Green colored herb, which boosts one's regeneration ability effectively healing around one third of character health.
Red Herb: Red looking herb, doesn't do any specific things on it's own, may react to use with different substances.
Blue Herb: Blue colored herb, rich in active minerals which force almost any kind of poison out of user's body.
