To change the things you are suggesting you will need to modify the JSP pages. All styles and colours etc. are defined in CSS which are defined in /projects/web-client/source/web/css/main.css.
To change the logo you will have to change /projects/web-client/source/web/jsp/parts/titlebar.jsp and to change the look of the login page you will need to alter /projects/web-client/source/web/jsp/login.jsp
Hope that helps.
