TL;DR:
Microsoft are introducing an improved left navigation in OneDrive for web and minor colour, font, and icon changes to the user interface. Due late July to late August 2023.

Details:
1. The background of the web app will be grey, instead of white. Your files in the main area will keep a white background

2. The bar at the top will also change to grey, from the current blue:


3. The ‘+ New’ button moves to the left navigation and will be labelled ‘+ Add New’

4. The ‘Upload’ button (file and folder) becomes an option within the revised ‘+ Add New’ button:


5. You will be able to expand and collapse the left navigation:


Availability:
Due late July to late August 2023.

Source, related links, and references:
MC626572.
Microsoft 365 Roadmap ID: 146071 and 146068.

Page originally published:
6th July 2023 and kept up to date.