\definefontfeature[default][default][expansion=quality]
\definefont[myfont][Serif*default]
\setupalign[hz]

% \setupbars[unit=pt,rulethickness=5]

\starttext

    \myfont \setupinterlinespace

    \underbar{\dorecurse{5}{\color[red]{\input knuth }}}

\stoptext
