The Unnamed Yellow Vessel was a transport-type ship in the Twelve Colonies of Kobol.
At least two had survived the attacks but one was left behind to be destroyed by the Cylons.
The FTL capable one was seen throughout the fleet, orbiting with Galactica, Gemenon Traveller (Flesh and Bone) or Prometheus (Black Market). It was orbiting Cloud 9 when Gina's nuclear bomb destroyed the luxury liner and three surrounding vessels, including the yellow vessel. (Lay Down Your Burdens, Part II)