Can customers be filtered by how overdue their invoices are? i.e. show customers over 90 days in red, over 60 days in blue, etc? I tried the aged buckets but they all show zero even though there are plenty with amounts in over 30, over 60, over 90.

Yes. There are two different ways this can be done. Check out the recorded webinar for Receivables 9.0B for more details on how to do this by either method.