Recently (the last week or so) I've noticed that my Tagged emails are no longer showing their respective colors. I believe this happened after Thunderbird was upgraded to version 68.2.2 (64-bit), running under Linux Mint 19.2 Tina
64-bit.
On a hunch, I decided to disable Reminderfox and reboot Thunderbird. Once Thunderbird was restarted, the Tagged emails again displayed their colors.
If I disable Reminderfox and reboot, the Tagged items again lose their colors.
So it appears there's some conflict between Thunderbird and Reminderfox.
Charles Heineke