color definition fails if a target model is set

[u-fischer]

xcolor allows to define a color in one model with values from another model. This fails if a specific target model is set with a package option or with \selectcolormodel

\documentclass{article}
\usepackage{xcolor}
\makeatletter
%defines the equivalent rgb color to the Hsb values
\definecolor{red1}{rgb:Hsb}{0,0.67,0.26}
\expandafter\show\csname \string\color@red1\endcsname 

\selectcolormodel{cmyk}
%\def\XC@tgt@mod#1{#1} %reverts the model selections
\definecolor{red2}{rgb:Hsb}{0,0.67,0.26} % errors
\begin{document}
blub
\end{document}

! Package xcolor Error: Undefined color model `rgb:Hsb'.