\setuppapersize[S4]

\definelist
  [MyTopics]
  [criterium=all,
   alternative=command,
   command=\TopicEntry]

\starttexdefinition unexpanded Topic #1
    \writetolist[MyTopics][location=none]{#1}{}
\stoptexdefinition

\starttexdefinition unexpanded TopicEntry #1#2#3
    \quad
    \doifelseincurrentlistentry {
        \bf
        \color[red]{#1}
    }{
        #1
    }
    \quad
\stoptexdefinition

\startsetups TopicFooter
    \switchtobodyfont[8pt]
    \placelist[MyTopics]
\stopsetups

\setupfootertexts
  [\directsetup{TopicFooter}]

\starttext
    \Topic{First}  First  Topic \page
    \Topic{Second} Second Topic \page
    \Topic{Third}  Third  Topic \page
\stoptext
