Potions are randomly generated consumables which spawn in the dungeon. They can drop after killing an enemy, clearing a room, breaking a pot, or by a familiar (such as the potion salesman). These potions listed are all the options available

Warning: Potions color is randomly determined upon creation, thus the color of a potion has no bearing on its effect.

Potion Cheat Sheet (by LazyGazelle)
Good Bad
Vigor: Health Up Lethargy: Health Down
Strength: Damage Up Limitation: Range Down
Quickening: Bullet Speed Up Weakness: Damage Down
Haste: Speed Up Latency: Bullet Speed Down
Blitz: Attack Rate Up Sloth: Speed Down
Entry: Doubles Keys Abeyance: Attack Rate Down
Molotov: Doubles Bombs Refusal: Lose All Keys
Wealth: Doubles Money Foiled Plot: Lose All Bombs
Vision: Reveals the Current Map Destitude: Lose All Coins
Vitality: Full Health Teleportation: Teleports You to Random Room
Defense: Spawns 2 Armor Nitroglycerin: Spawn 12 Live Bombs

*Please be aware that the potions being good or bad are completely subjective and can be used vice versa depending on your intention.