username colour changing

Making it flash would (i believe) require some javascript, which is a bad idea there. If you google "CSS flashing text" there are a bunch of threads about it. It'd only work in select browsers, and usually require JS.

On the other hand, changing it to a single color is easy. Create a new usergroup for him, making sure to set the permissions accordingly, and then in Usergroup Options for that usergroup, change the Username HTML Markup fields to whatever you wish.

Easy way: Make the opener:

<"font color="red">

Closer:

</font>

Cleaner/better way:

Opener:

<span class="usermarkup">

Closer:

[/code]
</span>
[/code]

Then create a new CSS definition in your style manager for that markup.

.usermarkup
{
color:red;
font-weight: bold;
Text-Decoration: Underline;
}

I'd to that, then set a rank image for that usergroup with some kind of blinky goodness.