As a long time user, I've just moved Aqua Mail to a new phone, and I've actually been looking at the screens in the process.
In my Smart Folder, there are triangular coloured flashes in the Top Left corner. They are always Red, Pink or Green (although I may have configured these colours way way back in the mists of time...) and bear no relation to the specific colours that I have allocated to each of my 12 email accounts.
When I look at the same list of emails in a widget showing the Smart Folder, the same 3 colours appear, but this time as a rectangle on the Right hand side, above the Time. The colours are the same as before (e.g. if a message had a Red triangle in the Smart Folder, then it will be a Red rectangle in the widget).
What is this colour telling me?