Some I came up with while reading; I think some have already picked the same individuals:
TOS
*Mandala Flynn from 'The Entropy Effect'-Kadida or Rashida Jones
*Reese Diksen from 'Star Trek: Recovery'-Ellen Page
*Admiral Nogura-Clyde Kusatsu
TNG
*Vicenzo Farrenga-Isaac de Barkol
The last name definitely sounds African.
*Miranda Kadohata-Stephanie Jacobsen
The girl from BSG:Razor who is of mixed ancestry, and Australian. I believe they have her picture on Memory Beta as an idea for the character anyhow...
*Ensign Rosado-Rita Moreno
DS9
*Elias Vaughn-Burt Reynolds
Give the guy a role he and work with, and he'll do wonders....
*Prynn Tenmei-Sandrine Holt, Moon Bloodgood, Tia Cararre (sp?)
Some have mentioned Grace Park, but Park doesn't look 'mixed.' However, I recall Tia Cararre doesn't actually looked mixed either, and she portrayed a half-black/half-Asian-Japanese on the film 'Rising Sun'....soooo....