I'm plotting potential distributions on a cortical surface using TkSurfer. The color scale "Heat" gives the most comprehensible plots. However, I would like to have the maximum values to be plotted in red instead of yellow, and minimum in dark blue instead of light blue.

max    +threshold    0     -threshold       min          -> Overlay values
yellow    red         gray      dark blue     light blue   -> Heat colorscale
red        yellow      gray     light blue     dark blue   -> Desired colorscale

Is there a way to have the color scale like this? I tried the color scales  'green red' and 'blue red', however, when I select these scales the brain surface disappears. 

Thank you,
Zeynep.