Just to explain a little more about the “Red” bass notes.
Normally you would play the bass with the root key. E.g. the chord Cmaj, would have the bass at the Key “C”.
However, in order to add some more depth to a chord progression you can use other keys in the scale e.g. the 9th or 11th and use that as a bass note at a lower octave. I have many such chord progressions in my charts included in the package.
A simple progression is below.
If we play using the scale of C then the Bass root would normally be “A” and “F”. However the red indicates to play “D” and “G” instead. These notes should be played at an octave lower than the chord itself.