Highlight words in multiple files

Hey everyone. What I want to do and don't know how is to find and highlight these 2 words "game" and "player" in .txt files.

No richtext.

so mostly like this code:

private void button1_Click(object sender, EventArgs e)

{

this.openFileDialog1.Filter =

"TEXT (*.xml;*.txt|";

this.openFileDialog1.Multiselect = true;

this.openFileDialog1.Title = "My text editor";

DialogResult dr = openFileDialog1.ShowDialog();

if (dr == DialogResult.OK)

foreach (String file in openFileDialog1.FileNames)

try

{

StreamReader reader = new StreamReader(file);

string content = reader.ReadToEnd();

reader.Close();

content = Regex.Replace(content, "game", "gaming");

content = Regex.Replace(content, "player", "playing");

so mostly like this code, but not actually replacing the word, just find it and highlight it. Help ???