You can purchase King Tut thread at the source on line ..
Superior Threads. They are always adding new colors. If you do alot of quilting you may want to have their color chart .
Many quilt shops are carrying it as well , but some do not have all the colors that are available.
They also have one of the best invisable threads ( can take high heat).
I have used "tut" in my bobbin but only on a short arm... wonderful results.