Thanks to DavidRSM, I have improved the highlighted syntax script for bash, and now it allows many more key words. Simply it is necessary to add to the variable keywords the commands names that they find in /bin/, and /sbin/, You can add more key words concatenating them to the variable, this way:

keywords=$keywords`ls 'Commands directory'`
#!/bin/bash

rutaCodigo=`zenity --file-selection --title="Select a File"`
case $? in
0)
  keywords="alias bg bind break builtin case cd command continue declare dirs disown do done elif else enable-in esac eval exec exit export fc fg fi for function getopts hash help history if jobs let local logout popd pushd read readonly return select set shift suspend test then time times trap type typeset ulimit umask unalias unset until wait while"

 #Agrego mas palabras clave de los directorios sbin y bine, que contienen comandos.
 keywords=$keywords`ls /bin/`
 keywords=$keywords`ls /sbin/`

 # Para lo comentarios, el & hace que se escriba lo que coincidio con el patron
sed 's/#.*/&/' < "$rutaCodigo" > temp
 cp temp "$rutaCodigo"

  for word in $keywords
  do
#Busco en el texto, cada palabra clave contenida en keyWords, y le añado la etiqueta span
sed "s/b$wordb/$word/" < "$rutaCodigo" > temp
    cp temp "$rutaCodigo"
  done
rm temp
  ;;
*)
  echo "No se seleciciono nada.";;
esac