WoWDB

Bom'bay's Color-Seein' Sauce was purchasable from Ravika for 500 x  Kor'kron Oil during Patch 5.3: Battlefield: Barrens.  The toy is no longer available to players and is hidden in the Toy Box - you will only see it there if you have learned the toy.

The Toy Box allows players to store vanity items in a manner similar to companions and mounts, without requiring physical storage space. The Toy Box will accessible through the user interface, as part of what is currently the Mounts And Pets interface.  The Toy Box is account wide, so you will only need to have acquired Bom'bay's Color-Seein' Sauce on one character.

Edit:  The toy is once again available in the Legion expansion.  It is only sold by a Stormwind NPC.