The red note is the root note of the chord or arpeggio, for example:
– if you wish to play the A major triad then the red root note will be the note of A, for example, the ‘E’ shape for A major triad is at the 5th fret, the ‘A’ shape for A major triad is at the 2nd fret.
– if you wish to play the D major triad then the red root note will be the note of D, for example, the ‘E’ shape for D major triad is at the 10th fret, the ‘A’ shape for D major triad is at the 5th fret.
You can use MusicWheels™ to discover all the other major triads and arpeggios and their notes.