From Nielson Norman Group: https://www.nngroup.com/articles/branding-intranet/
Summary: The name of the intranet, its logo, and the visual relationship with the company’s external website are key elements to consider when establishing a brand and an identity for your intranet.
Most Intranets are created and owned by IT, HR, Corporate Communications, or a combination of these departments. While these teams have the necessary skills to create and maintain great intranets , they don’t usually include experts in branding. Thus, intranets frequently lack a brand identity. A weak or nonexistent intranet brand leads to poor credibility, adoption, and acceptance.
Any intranet team can improve the intranet branding by focusing on a few key elements —name, logo , relationship with the public-facing website — that can have the biggest impact.