We are often asked for an explanation of the various colours associated with the child's account screen.  Here's a quick summary:

Green - The invoice is fully paid, no outstanding balance.

Amber/Orange - This invoice is part paid, a payment has been made against it, but there is still a balance outstanding.

Red - The invoice is fully outstanding, no payments have been made against this invoice.

Brown - This means the invoice has been credit noted.

Black - This relates to all other transactions other than the ones mentioned above, such as payments and credit note details.