%ExchangeInstallPath%FrontEnd\HttpProxy\owa\auth\\themes\resources\logon.css
Customize the color of the Outlook on the web sign-in page Remember to backup your original and changed files to another folder so that you can replace them when you Update or Upgrade or if something goes wrong with the changes. NOTE: Every time you install an Exchange Cumulative Update (CU) or new version of Exchange Server these modified files will be replaced. Below is the process to do that effectively for your organization. I have changed the color on the left to match my scheme, replaced the Outlook Logo with my company logo, and added a disclaimer to notify users.
Here is what my company OWA page looks like: Customized OWA Logon Page Most companies, like myself want to be able to customize that page so that it suites your organization. As many of you are aware, Microsoft provides a default logon page for OWA, the Outlook Web App.