After making a potion or xmute, you see a flash, much like when you level or rep up and in the chat box it says....Discovery, You have just discovered how to make flask of coolness.  After which it appears in your recipe book.  Of the three I've now learned one was lettered grey at the time, one is yellow and one red.  I'm am a 375 alchemist, so I assume the red one is the most rare of the three.