[Chimera-users] Electrostatic Potential based on Poisson-Boltzmann using APBS

Dear chimera users, I am using chimera 1.10.1. I did following steps to obtain Electrostatic Potential based on Poisson-Boltzmann using APBS: open... pr.pdb action... surface... show to obtain *.dx file, I typed APBS in command line, after minutes, *.dx file was created and surface color window was opened, I pressed color tab. Please see the figure in following link: https://www.dropbox.com/s/99gjecypqu910hu/apbs.png?dl=0 Why are the colors black and white in the surface, instead of blue and red? Any help will highly appreciated.