Origin of the "Pink Slip"

[Barnhart]

An interesting question.  OED offers a quote from 1915 (confirmed by
W10):

And have Murphy hand me the pink slip tonight.  'B.L. Standish,'
_Covering Look-in Corner_, 1915

Neither this nor any of the other quotes in OEDs shows any evidence of
the term's origin.  The term is not in DA or DAE.  Who chose the first
piece of pink paper for this purpose I suspect will remain a mystery.
It was probably chosen in the later part of the 19th century in a
business where it was not particularly common and for the purpose of
not being "losable" on one's desktop.

Regards,

David K. Barnhart, Editor
The Barnhart Dictionary Companion [quarterly]
barnhart at highlands.com
www.highlands.com/Lexik

"Necessity obliges us to neologize."
Thomas Jefferson-August 16, 1813