Rated 4 out of 5 stars

per Alexander Ihrig el set. 10, 2020 · enllaç permanent

There is now a completely revised successor add-on that works really completely with Thunderbird 68. * and Thunderbird 78. *:

https://addons.thunderbird.net/thunderbird/addon/quotecolors/

Please note that the other / old variants of the add-on must be uninstalled!