could you be a little more explicit with your question and perhaps link to a page where you want to achieve the changes?
If you want to style elements differently on a specific page use the developer tools in chrome (right click-> inspect)to identify your page class, and choose your way (css plugin or child theme to implement css changes)
You will then be able to write css which targets elements only on that page e.g.
.page-id-3360 #branding img {
border-bottom: 25px solid #c5d74d;
}
