Tritone Substitution

So, here is a tritone substitution showing C7 to F#7. These chords share two notes.

You may want to read this: Wikipedia, Tritone Substitution

The fingering charts shown here work for improvisation between these two chords.

One could also start the F# chord at 7 (ie in the centre course) and the C chord at '5 to get more even a spread of notes around both roots. In fact, that would probably be a better approach.

I've probably missed a few of the blue notes as well but you get the idea. Corrections or additions are welcome