Here is the way to do it:

1. Go to the CDU, Options > Options > Page 2
Turn on "LOAD DEFAULT PANEL STATE"

2. Go to Prepar3D v4/Captain_Sim/767-II/Panel
Copy the "COLD AND DARK.cfg" file from the Basic folder into Custom folder. Then rename the file in your custom folder into DEFAULT.cfg

The 767 ( and 757 if you also have it as long as you do it in its own folder) Will now start Cold and Dark everytime.
 

another question.  When loading in Cold and dark can you turn on the flight computer to select a different panel state without turning on the battery etc.  I know other aircraft you can hold a certain button.