https://www.theverge.com/2018/11/29/18117580/microsoft-office-new-icons-2018-design-features

Microsoft is modernizing its Office icons as part of a broader focus on design for its various Office apps. It’s the first time the Office icons have changed in five years, and they’re designed to be more simple and modern to span across multiple devices and platforms. Office now exists on Windows, Mac, iOS, and Android, and Microsoft has been building a single core codebase to make rapid monthly improvements to the apps. These icons are designed to reflect how Office has changed recently, with new AI features, more collaborative features, and its platform independence for key apps like Word, Excel, PowerPoint, and Outlook.

The new icons deemphasize the letter for each Office app, but still manage to look familiar. “Our design solution was to de-couple the letter and the symbol from the icons, essentially creating two panels (one for the letter and one for the symbol) that we can pair or separate,” explains Jon Friedman, partner director of design at Microsoft. “This allows us to maintain familiarity while still emphasizing simplicity when inside the app.”