How to change your jenkins theme

Why? 

Because I have two environments: development and production. They look very similar and I don't whant to broke production environment during testing

How?

1) Install theme plugin

 

 2) Add your css and js (and img) files under %JEKINNS_INSTALLATION_PATH%/userContent folder

 3) Add links to these files in configuration

 

4)* You may left blank field with JS file if you don't have one

 

What I've got?

With css below 

 #top-panel > * {
    background-color : #B80000 !important;
 }

I've got this result