changing the appearance for single dots in fret boards

[Marc Hohl]

Hi list,

I have some fret diagrams where one dot is placed and removed according
to the underlying rhythm, so it would be great to either change its
color or put it in parentheses.

In the example below, I want to change the appearance of the dot created 
by (place-fret 4 5 3).

Is that possible somehow?

Thanks in advance,

Marc

---

lower = {
  d g\4-3 d g\4

upper = {
  d'-1 h\3-2 d' h\3 d' h\3 d' h\3
}

fretboard = {
  s1^\markup {
       \fret-diagram-verbose #'((mute 6)
                                (mute 5)
                                (place-fret 4 5 3)
                                (place-fret 3 4 2)
                                (place-fret 2 3 1)
                                (mute 1))
     }
}

\score {
  \new Staff {
    \key g \major
    \clef "G_8"
    <<
      \new Voice { \fretboard }
      \new Voice { \voiceOne \upper }
      \new Voice { \voiceTwo \lower }
    >>
  }
}