The flavoring used in
ejuice is food grade flavor that is the same that is used in foods such as candy, frosting even coffee. You can get different brands from many different vendors. Most flavors have PG added and some have coloring added. But like Hoosier said, you really should read the DIY guide that he linked above.
A side note...be careful about buying grocery store flavoring because some add oils and other additives that could gunk up your coil faster and may not be as healthy.