The same way you acquire green ones. They're just rarer.
Or you can buy them in the guild store or through players in zone chat.
ClaudiaMay wrote: »
ClaudiaMay wrote: »
Just for reference - by level 19 i have found two blue recipes, on a character that absolutely HAS to open and loot every crate and bag she comes across Must have opened thousands by now.
So they are fairly rare.