RLS and paginated reports

Hello

I have a paginated report set up and i'm now trying to implement RLS on this by following this micrsoft article:

https://learn.microsoft.com/en-us/power-bi/paginated-reports/paginated-reports-rls

However, i don't really understand the context of this article.  In their example it's using WHERE FinalTable.Color = @UserID but i dont understand this as a colour e.g. red would not match to a user ID.  Can anyone explain this better?

Also once this is working, how do i test it.  With power BI you can go to security on the dataset and view as a user from there.  My paginated report is using a dataset within a workspace but i dont understand how to test as another user.  The article above make no mention of this.

Thanks in advance.