please provide the forum url... css changes are easier to fix with the forum url...
if you want to change the color of that specified forum (in the image) only, then add the following code to global.css of your theme...
tbody#cat_11_e tr:last-child td strong a {color: #FF0000;}
Ye, i added but i couldnt understand what it exactly did, nothing changed.
He just changed the color of the text.. he was just showing you how to change it.
If you do not know HTML/CSS I would recommend just installing a theme, which can be found
here. (Just press "extend" at the top of this page)