Last year we announced that Office Fluent Design would expand to OneDrive for the web and align with the entire Office 365 suite on a common color palette, typography and icon systems. We introduced a shared header seamless across products, with elements thoughtfully aligned to focus on what matters. As we continued to roll out the Fluent Design system and the revamped Office brand icons, we also updated the file folder representation, unveiling golden folders across web and mobile.
Today, we carry forward this broad design overhaul to mobile and are excited to share the refreshed look and feel of the OneDrive mobile app. We, too, are updating how you work with recent files, annotate PDFs, link to files via Outlook mobile and more.
Source: Designing a Fluent Microsoft OneDrive Mobile Experience – Microsoft Tech Community – 757716