the hairs turn amber at perfect ...and when I say perfect I don't mean ideal stone, I just mean, speaking in gardening...fruit terms, or whatever, that they will be as potent as possible with the highest thc content and when the hairs all turn a burgandy or even darker in some strains then you've waited too long. It's still weed, but I don't think you'll appreciate as much..If I were your friend, and this is just me, but I would harvest when the trichomes are a milky colour, because I prefer the head high. Ask him if he wants to go to bed or actually make something of his impairement, and if it's option #2 then maybe go with my desired harvest time. To each his own though, and a couch lock is better for medicinal users.