Problem coloring Ambitus ledger-lines

[Patrick Karl]

The following MWE:

\version "2.19.38"

music =  { c'4 c''' r2 }

\score {
    \new Staff \music
    \layout {
       \context { \Staff \consists "Ambitus_engraver"
           \with { \override AmbitusNoteHead.color = #red
                      \override AmbitusLine.color = #red
%                     \override LedgerLineSpanner.color = #red
           }
       }
    }
}

seems to illustrate a problem with Ambitus, namely, there doesn't seem 
to be a way to change the color of ledger lines within the Ambitus.  The 
output of the above snippet is attached; it shows the Ambitus ledger 
lines as black.  Uncommenting the "\override LedgerLineSpanner.color = 
#red" statement changes the color of not only the ledger lines within 
the score, but also within the Ambitus.

It looks like there should be a grob, AmbitusLedgerLineSpanner, 
independent from LedgerLineSpanner.  Or am I overlooking something?

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