External Email - Use Caution        

Dear all,
I am studying transcranial magnetic stimulation (TMS) and would like to nicely visualize my TMS induced electric fields over a pial surface, preferably using Freesurfer to stay in line with my other images. I have a .nii file of the electric field distribution, registered to T1, representing field strengths in every voxel. Visualization in freeview looks okay, but visualization using tksurfer does not really give the right results (most of the brain is yellow... no field distribution visible). I guess something goes wrong in the setting of the colorbar. Preferably I would like to see the field strengths (min:max) in a blue-red colorscheme. Can anybody tell me how to accomplish this?
Thank you very much in advance.
Best,
Debby