MyBB Community Forums

In my forum, I have a specific forum which is access restricted to some users.
I would like to change the header color of this forum only, in order to make it more visible among the other ones to those who have access.
The other forums should stick on the actual color, without any change.

I searched here but could not find anything.

Thanks for your help.

In the forum's settings you can define a style/theme for a (sub) forum and check a box to override the users' theme choice.