\documentclass{article}
\usepackage{pdfresources,l3pdf}
\usepackage{l3draw,l3color}
\ExplSyntaxOn
\color_model_new:nnn { BarTone } { Separation }
{
name = BarTone~555~GN ,
alternative-model = cmyk ,
alternative-values = { 0.1 , 0.2 , 0.3 , 0.4 }
}
\color_set:nnn { BarToneTest } { BarTone } { 0.5 }
\pdf_uncompress:
\ExplSyntaxOff
\begin{document}
\ExplSyntaxOn
\draw_begin:
\draw_path_moveto:n { 0cm , 0cm }
\draw_path_lineto:n { 1cm , 1cm }
\draw_path_lineto:n { 2cm , 1cm }