Purple Book
= P =
push
purple wire n.
[IBM] Wire installed by Field Engineers to work
around problems discovered during testing or debugging. These are
called `purple wires' even when (as is frequently the case) their
actual physical color is yellow.... Compare blue wire,
yellow wire, and red wire.
--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.