If you got this error:

! Undefined control sequence. <argument> ... }{\mddefault }{\updefault }{\color [rgb]{0,0,0}$some_latex_text$}} l.xx }}}}

or

./directory/figure_file.pdf_t:line_number:Undifined Control Sequence }}}}

(in Kile for example)
It's becauce jinst.cls class does not understand (or has a wrong interpretation) of the \color LaTeX command. Just add:

\providecommand{\color}[2][1]{}

This will do the job !

Be careful: not tested if the LaTeX text inside the figure is not in black !

In addtion, it seems that jinst class and subfig package are not compatible. I use subfigure instead, but this page gives the following solution:

\usepackage[caption=false]{subfig}
% Make \subref robust
\makeatletter
\AtBeginDocument{%
\DeclareRobustCommand*\subref{\@ifstar\sf@@subref\sf@subref}}
\makeatother

source