Hi,
I can not find any keyword must be used to get what I want.

Thanks,

Fabrice

\setupbodyfont[pagella,11pt]

\setupitemgroup
  [itemize]
  [each]
  [color=darkred]
  [packed]

\starttext

\startitemize[n]

\item \input tufte

\item \startitemize[a]

\item \input tufte

\stopitemize

\stopitemize

{\tfc What I want to do :}

\blank

{\darkred 1.} \input tufte

{\darkred a.} \input tufte

\stoptext