The Ayurvedic text, Bhavapraksha describes three varieties of sesame: black, white and red.

"Of these black is regarded as the best suited for medicinal use.  White seeds are of intermediate quality."  

Tri Health recommends that you purchase thailams containing black sesame.

Sesame is regarded in Ayurveda as a super seed and, in India, was one of the first ever seeds used for oil production.  In India 'til' means oil, originating from and the sanskrit word for sesame 'Tila'.

"Tailas (oils) are generally similar (in properties) to their source (oil seed), of them the chief is that of tila (sesamum).

Oil of sesamum possesses the properties like penetrating deep into the tissues, …and spreading throughout the body fast.   (55-56)

"The term ‘taila’ specially means the oil of tila (sesamum) and used in that sense itself at all places in all the ancient books of Ayurveda (and even Sanskrit literature) unless specified differently.  In the context of Ayurveda, it is sesamum oil that only should be used for internal administration of medicated oils."