Microsoft officially announced on August 2 the public preview of its new login experience for the Azure Active Directory and Microsoft Account. The goal is to converge both account identity systems and the redesign of the sign-in UI is a major step towards consistency.
Also, companies will be able to configure customized login pages using existing company branding, if configured. This includes the sign-in image, banner logo, username hint, sign-in page text, and background color.
Furthermore, changes to the mobile sign-in UI are also rolling out, including the ability for companies to customize it, as can be seen from the image above. The whole redesign will continue as an opt-in public preview for the next few weeks and the final switch over is planned for the last week of September. Finally, Microsoft notes some pages will still show the old design for some time, such as those related to Microsoft Multi-Factor Authentication service.