'Bivariate Granger Causality(spectral)NxN' in Connectivity

Dear professor, and others whom it may concern,
I came acorss a little problem when using the function of 'Bivariate Granger Causality(spectral)NxN' in Connectivity.
Firstly, The results make me confused. There are two main colors, the red and the blue, between two nodes. I wonder is the blue gradully changing to red representing the cause to result? I can't tell the causal relationship between them.(A figure is attached).
Secondly, wether any models like multi-variant autoregressive models or not are used in Granger Causality?
Thirdly, when using the Granger Causality to analyse the connectivity between two channels, which time scope is recommeded under the different sampling rate?
Best Wishes
Zhexue.

The results make me confused. There are two main colors, the red and the blue, between two nodes. I wonder is the blue gradully changing to red representing the cause to result? I can’t tell the causal relationship between them.

In this figure, the changing color represents the direction of the interface: from blue to red.

Secondly, wether any models like multi-variant autoregressive models or not are used in Granger Causality?
Thirdly, when using the Granger Causality to analyse the connectivity between two channels, which time scope is recommeded under the different sampling rate?

@Sylvain @leahy @hossein27en @Guiomar ?

I am not sure about what you mean exactly. I recommend you use parameters that have been published in journal articles and reporting on using Granger measures.