There are a few ways to transform to Talairach space from MNI space.
# for N27 in MNI (MNI_N27) space data, this works best
adwarp -prefix tt_testmni_region -resam NN -apar TT_N27+tlrc -dpar testmni_regions+tlrc. -force
# Use the two-part Brett transform for the ICBM452 or MNI-152 datasets, this probably works better
3dWarp -mni2tta -NN -prefix tt_testmni_region_brett+tlrc testmni_regions+tlrc.
# color in AFNI with separate colors per region
3drefit -cmap INT_CMAP testmni_regions+tlrc.
3drefit -cmap INT_CMAP tt_testmni_region*+tlrc*.HEAD
You could also use the Lancaster transformations too. See this previous post for some gory details. Check your results in the afni GUI.
https://afni.nimh.nih.gov/afni/community/board/read.php?1,75269,75394#msg-75394
