I would say,
N,N-DMT (White) is the purest form.
Spice (Yellow, Orange, Amber, Red, Brown) is a collaborative array from all the psychoactive alkaloids of Mimosa Hostilis which can yield a particularly different yet similar experience as opposed to pure N,N-DMT. It still contains N,N-DMT but as stated above, has a spectrum of other alkaloids.
Salvia to me is similar in some ways in that it can rip you from your body, but feels dirty and un-educational, and not nearly as overall beneficial as N,N-DMT or Spice.