Rated 5 out of 5 stars
Please have a look at the Thunderbird error console. There are hundrets of entries for "account colors". This might also be the reason why account colors is sometimes not working correctly after a restart of Thunderbird, so that the Add-On's settings must be set again.
This is probably caused by interaction with another add-on that uses the custom column handler interface. Please can you tell me which other add-ons you are using.