Color parenthesized accidentals with \accidentalStyle teaching

[Paul Morris]

Just in case anyone is wondering, `AccidentalCautionary` is the GROB to 
override to color the parenthesized accidentals you get with 
`\accidentalStyle teaching`.

-Paul


%%%

\version "2.21.0"
\new Staff {
  \key g \major
  \accidentalStyle teaching
  \override AccidentalCautionary.color = #red
  { fis' f' }
}

%%%