In the "FreeSurferColorLUT.txt", what brain regions are represented by "right-vessel" and "left-vessel", respectively? Is there a file or document that explains the definition of regions listed in "FreeSurferColorLUT.txt"?

Also, the atlas for subcortical segmentation is in $FREESURFER_HOME/average/RB_all_2008-03-26, which is a ".gca" file. What is this format? Is there a way that I can "see" this atlas in 3D? Can it be transferred to a ".nii" file? 

Thanks,

Xinyang