from
Jargon File (4.4.4, 14 Aug 2003)
blue wire
n.
[IBM] Patch wires (esp. 30 AWG gauge) added to circuit boards at the
factory to correct design or fabrication problems. Blue wire is not
necessarily blue, the term describes function rather than color. These
may be necessary if there hasn't been time to design and qualify
another board version. In Great Britain this can be bodge wire, after
mainstream slang bodge for a clumsy improvisation or sloppy job of
work. Compare {purple wire}, {red wire}, {yellow wire}, {pink wire}.