Just create the calculated field [New] returning simply 'New' in a file 2,
(or if you already have the field like this, you don't have to create any more)
and put it into color.
Thank you for your assistance. I've added an example workbook. I am not sure I understand how returning new in the 2nd file will identify the accounts as new from file 1. NOTE: This example does not have the same measures as the screenshot but does provide the same challenge.
It is defined by the link icon and relationships.
Tableau joins the data sources using the field which link icon is active as the key.
If the field name of the join key is not the same, you can edit relationships manually.
Does this answer your question?