If your client adds new color flags to your files or changes or removes existing ones, you will always receive an email. All new color flags or changes to existing color flags are listed in this mail. Existing color flags that have not changed are not listed there. You can view them at any time in the gallery. The email is always sent 5 minutes after the last color flag was changed.
If you no longer want to receive these emails anymore, you can deactivate them in the notifications section of your account settings.