It shows connections FROM the lowest color in the colorbar TO the highest.
We are in the process of updating these tools. Major updates to the display of these connectivity graphs will be pushed in the next few days.
https://neuroimage.usc.edu/brainstorm/Tutorials/Connectivity2#Granger_Causality
https://neuroimage.usc.edu/brainstorm/Tutorials/ConnectivityGraph#Filtering_options