Entrance of Silver Canyon. However, you should get the reactor to increase drop rate before doing so. This reactor should be at floor 8 or 9, then you can link it up to floor 7 and straight into Silver Canyon.
When farming a particular color always throw down that particular hex color on the area your farming, it counts as an extra drop that can occur.
What I'm still wondering is, does it become an enemy drop or a "battle" drop? Point being, do you have more chance to get them with bonus shots, smackdowns and breaking or should you just do leader assaults when you can?
i'm pretty sure its both but the drop is better if you do the smackdowns and bonus shots - i was farming purple hexes and just doing bonus shots and i always get 1 or 2 from the guards from Patar's dungeon.
i am having trouble getting green hexes too... got into canyon and keep facing rogue with wolf or rogue with gremlin and i get maybe a green every 3 battles - i do get yellow hexes but not what i need. I understand i am supposed to link the terminal for more chances BUT i dont see that happening since i only have 12 green hexes and need 5 to convert to a station and i gotta start the station back from entrance... am i doing something wrong or just bad luck? i get similar encounters out of canyon too...