Code:
on $^*:text:$($+(/\b,$me,\b/i)):#:{ 

  ; Change this line if you wanna change the colour:
  var %c = 4

  echo -bfilmrt # $nhighlight($1-,%c)
  haltdef
}

alias nhighlight {
  var %c = $2
  return $regsubex($1,$+(/,$chr(3),(\d{1,2})(.*?)\Q,$replacecs($me,\E,\E\\E\Q),\E/gi),$+($chr(3),\1\2,$chr(3),%c,$me,$chr(3),\1))
}


Simples.

Doesn't take background colours into account, let me know if you need that adding.