No Update for TB6? Rated 4 out of 5 stars

Not a review, but if this isn't updated to TBird>3, you can find a similar function (and more) in 'identity-chooser'.

https://addons.mozilla.org/thunderbird/addon/identity-chooser/

This review is for a previous version of the add-on (3.3). 

Version 4.1 is compatible with Thunderbird 5.* and 6.*

Account Colors Version 4.1 is compatible with Thunderbird 5.* and 6.* and is available for download as an experimental version, pending formal review and release. To download Version 4.1, scroll to the bottom of this page and click 'Version Information', then click on the 'View all versions' link, then click on the 'Download Now' button for Version 4.1.