I am an enterprise client trying to use custom branding and I find the current limitations very disappointing.

Firstly, the fact that you can add a custom color as the color scheme for new users, but I cannot choose it as an existing user is completely baffling. That means all internal demonstrations and training content are going to be mismatched for ever more with no un-do. Why is it set up that way? If there's any reasoning or remedy I haven't found yet, please advise.