The treble clef "G" is the chord member of the C major chord.
The term "major chord" in art does not have a specific meaning. In music theory, a major chord is a chord consisting of a root note, a major third, and a perfect fifth.
However, in the context of art, the term "major chord" may be used metaphorically to describe a composition or artwork that is harmonious, balanced, and pleasing to the eye.
This means that it is one of the three notes that make up the chord: C, E, and G.
Passing tones and neighbor tones are non-chord tones, which means that they are not part of the chord.
Passing tones move between two chord tones, while neighbor tones move from a chord tone to a neighboring note and then back to the chord tone.
Therefore the treble clef "G" is the chord member of the C major chord.