A spot color is one that is printed with its own ink. 
Typically, printers use spot colors in the production 
of books or other printed material. The spotcolor package
by Jens Elstner is a first attempt to introduce the use of 
spot colors with pdfLaTeX. The xespotcolor package is a 
reimplementation of this package so to be usable with 
XeLaTeX or LaTeX+dvipdfmx. As such, it has the same user 
interface and  the same capabilities. Version 2.0a added
support for the xcolor package and so one can use
spotcolors in TikZ pictures. In this version one can 
safely use spotcolors with the tcolorbox package and
I have updated the package so to use the correct shipout
hook provided by the LaTeX kernel.
 
Apostolos Syropoulos
2021/03/01