We want to customize the landing page with gray background with a client specific brand and also customize the thin vertical bar, top navigation etc in 6.4. Is there documentation that explains what components we need to overlay etc?
The background of the "Navigation" landing page (Page you see as soon as you log into AEM) - you need to create a clientlibs category of foundation granite/ui/components/coral/foundation/clientlibs/foundation.css
The vertical bar that has navigation and tools button - You can do it CSS, instead of icomoon you can use Text or image which has your brand name with text
To change The top bar that reads "Adobe Experience Manager" you need to overlay /libs/granite/ui/components/shell/page/page.jsp