> lower = \relative c {
> \override Fingering.color = #red
This line could be changed to read
> \override Staff.Fingering.color = #red
which “speaks” to the right context.
You could also replace the two \override with something like this:
> \score {
> \new PianoStaff <<
> \set PianoStaff.instrumentName = #"Piano "
> \override PianoStaff.Fingering.color = #red
which affects all the Staff contexts included.
Cheers
Francesco Napoleoni
