Your users, staff and students will regularly be viewing your IdP login page. They will also be using other sites within your organisation. To ensure that your users will be comfortable entering their username and password the login page should have the same corporate colours and fonts scheme as in general use across the rest of your organisation.
Recommendation: The AAF Recommends that your IdP user interface has similar corporate branding to the rest of your site.
A number of organisations have just replaced the Shibboleth logos with their corporate logos and stopped there. Your web team should be consulted on the design and layout of your IdP to ensure it is consistent with your entire site so your users are comfortable using the site.