Unfortunately it's not quite that simple. You need to put HTML "font" tags around the text you want to highlight. It's not possible to type in the real code as you wont see it, but if you copy the next line and then paste it into a reply window, the text will appear italic, bold and red in your post.
<font color="red"><i><b>This text will be red, italic and bold.</b></i></font>
Remember that all HTML tags must be nested. In other words, the closing tags must be in the reverse order of the opening tags or it won't work.