Change style FacesMessages

You can manipulate almost all elements of the screen just by inspecting elements with the firebug or tools of the browsers themselves, an example if you wanted to change the error messages, would be:

.ui-growl-error, .ui-growl-fatal, .ui-messages .ui-messages-error, .ui-message.ui-message-error, .ui-messages .ui-messages-fatal, .ui-message.ui-message-fatal {
        background-color: #FFFFFF;
        border-color: #red;
        color: #000000;
    }

This is the part that displeases me in these beans for faces, always need to be overwriting CSS, and often need to force CSS to use the! important property, but anything can be done.