Customize thread color

[Beardy]

Where I can find tutorial, how to config [thread prefixes]?

It's pretty straightforward: ACP > Configuration > Thread Prefixes > Add New Thread Prefix.

Then just fill out the form, writing your prefix into 'Display Style'. HTML is accepted in that field, so you can either style it with inline CSS or give it a class and style it through a stylesheet.

You might also want to limit the groups that can use it by clicking on 'Select groups' under 'Available to groups'.