It should. You can also move the override of BarLine later as I do below.
I believe the issue here is that the barline is considered to _begin_ the new measure rather than end the old one. I can't think of a way around this except what James suggests. (Then there's the issue of the staff lines underneath the bar line, to which I don't have a ready answer.)
BTW, your bars don't all add up.
\version "2.14.2"
#(set-global-staff-size 18.65)
\header {
title = "System in different colors"
}
\language "deutsch"
staffVoice = \new Staff {
\set Score.tempoHideNote = ##t
\time 2/2
\key f \major
\clef treble
\tempo 2=78
\relative c' {
\context Voice {
\override Staff.Clef #'color = #red
\override Staff.TimeSignature #'color = #red
\override Staff.KeySignature #'color = #red
\override NoteHead #'color = #red
\override Staff.StaffSymbol #'color = #red
\override Stem #'color = #red
\override DynamicText #'color = #red
\override Tie #'color = #red
\override TextScript #'color = #red
\override Staff.BarLine #'color = #red
\override Staff.LedgerLineSpanner #'color = #red
\partial 4*3
<d' b>4^\markup{ \larger {Part 1}}_\f <c a>
f4
\stopStaff
}
\context Voice = "melodyVoi" {
\dynamicUp
% \partial 4*3
\startStaff
\revert Staff.Clef #'color
\revert Staff.KeySignature #'color
\revert Staff.BarLine #'color
\revert Staff.LedgerLineSpanner #'color
\revert Staff.StaffSymbol #'color
\revert NoteHead #'color
\revert Stem #'color
\revert Tie #'color
\revert DynamicText #'color
c4\(_\mf h c\)
\bar "||"
<f c> <f c> <f c> <f c>
<f c> <f c> <f c> <f c>
<f c> <f c> <f c> <f c>
<f c> %% ?????
}
\context Voice = "melodyRep" {
f1 R1
\bar "|."
\stopStaff
}
\context Voice = "interlude" {
\startStaff
\override Staff.VerticalAxisGroup #'remove-first = ##t
\override SystemStartBar #'color = #black
\override Staff.StaffSymbol #'color = #red
\override NoteHead #'color = #red
\override Stem #'color = #red
\override DynamicText #'color = #red
\override Tie #'color = #red
\override TextScript #'color = #red
\override Accidental #'color = #red
\override Rest #'color = #red
\override Staff.LedgerLineSpanner #'color = #red
f4^\markup { \larger {Part 3 }} e f g
\override Staff.BarLine #'color = #red %% I moved this
c,4 r <h f' g> r
\bar "||"
}
}
}
\score {
\staffVoice
\layout {}
}
\paper {}