Colour blind palette theme

Hi,
We have some staff members with sight impairment and also colour blind.

I noticed that there are already some properties that you can add to the user page so it can be selected for certain users. But selecting any of these options and saving does not do anything.

How can I get these options to work? Are there specifically themes that need to be added to each environment? Is the theme automatically going to work once you install it and select for a specific users?

I cannot find any information or instructions on that. It will be very much appreciated for a few of our staff members.

Thank you,
Luciane Szabó