Blu.7z -

It could simply be a manual backup created by another user who named it "blu" for personal organization. How to Open blu.7z

A 7z file is a compressed archive. It uses advanced LZMA compression to shrink large files much more effectively than the traditional ZIP format. It’s open-source, supports massive file sizes, and is frequently used by developers to share code or assets. What Does "blu" Stand For? blu.7z

Since Windows and macOS don't always support 7z files natively for extraction, you’ll need a third-party utility: It could simply be a manual backup created

Once installed, right-click the blu.7z file. supports massive file sizes