there are 3 kinds of soulstones . (not counting fragments)
Red : these come as veterin rewards and show up as soulstones , not tokens . only the one who claims the reward can use them.
Green : these are purchased from EA for 10 bucks . they come as a token anyone can use . once the token is cashed in it becomes a soulstone only the one who cashed in can use.
Blue : these are quite rare . originally the 7th aniversery addition (7AE) promotion gave out blessed amber leggings and samauri helms . people went up in arms over something blessed on siege , so they created 7AE trade in guy who would take the blessed legs or helm and give you a token for a soulstone (which came out blue) .
i dont know any other way you can get blue soulstones you can use unless you get one of these very rare tokens.
if what you want is a soulstone you can use , id look for a token for a green one . people sell them for 2.5 to 3 million each or you can buy a legacy token that gives green soulstone for 9.99 here .
http://www.uogamecodes.com/store/prod_detail.asp?ProdID=UOLGCYTKN&CartID={162952D6-3B95-481C-B40E-559E453FEAA0}&PromoID=996
if you specificly want a blue one ? ... well ... good luck with that.
edit i do recall a long while back there was a preorder promotion ... mondanes legacy i believe , that gave out soulstone tokens. these MIGHT have been blue , but i dont know . i waited too long to turn in my codes and they tell me the codes are no longer valid. *shrugs*