How do you flag new common ancestors?

[Phoenix]

I check weekly and, as is to be expected, rarely get new matches. But, to keep tabs on them, and quantify them, I also colour code them. Every so often, I filter common ancestors and check whether I have my colour spot by them. Invariably, I find new names. If I (or the match) adds to our trees, Ancestry does not think it is "new" so does not bring it to my attention.

Best Mate has over two hundred matches with common ancestors, so checking the list is a task and a half. Can anyone think of a better way?

Oh, and inevitably I have several false ancestors, as there are errors in trees. Cousin is apparently not black now, but Jewish.