Hi Aaron,
Wow, that technique for overriding end-of-system / begin-of-system grobs *independently of one another* fills in an extremely important LilyPond gap for me.
I've modified your example for the archives; everyone should know this technique.
%%% INDEPENDENT LINE-BREAK OVERRIDES %%%
\version "2.19.83"
\new Staff
{
\omit Score.BarNumber
\omit Staff.Clef
\omit Staff.TimeSignature
c'4 c'4 c'4 c'4
\bar ":..:"
\once \override Staff.BarLine.color = #(lambda (grob)
(if
(eq? LEFT (ly:item-break-dir grob))
(set! (ly:grob-property grob 'color) red))
(if
(eq? RIGHT (ly:item-break-dir grob))
(set! (ly:grob-property grob 'color) blue)))
\break
c'4 c'4 c'4 c'4
}
\layout {
indent = #0
ragged-right = ##t
}
%%% END %%%
Trevor.