\definestructureresetset[default][0,0][1]
 
 \setuphead
    [part]
    [style=\ss\bfd,
     resetnumber=no,
     conversion=R,
     sectionresetset=default,
     placehead=yes]
 
 \setuphead
    [chapter]
    [style=\ss\bfc,
     sectionsegments=2:100,
     resetnumber=no,
     color=TheColor]
 
 \setuphead
   [section]
   [sectionsegments=2:100,
    style=\ss\bfb]
 
 \setuphead
   [subsection]
   [sectionsegments=2:100,
    style=\ss\bfa]
 
 \setuphead
   [subsubsection]
   [sectionsegments=2:100,
    number=no,
    style=\ss\bfa]
\starttext

\placelist[part,chapter,section,subsection][criterium=all]

\part{first}
  \chapter{alpha}
    \section{a}
    \section{b}
      \subsection{x}
      \subsection{y}
  \chapter{beta}

\part{second}
  \chapter{gamma}
    \section{a}
    \section{b}
      \subsection{x}
      \subsection{y}
  \chapter{delta}

\stoptext

