Rated 4 out of 5 stars

I tried all the tab-coloring extensions I could find (three), and I like HashColouredTabs+ best.

ChromaTabs refuses to apply URL-based colors until the tab is brought forward or moused-over. This has gone unaddressed for a while, so it doesn't seem to be currently supported. And Firefox 2.0.0.10 broke it completely (though a later nightly build reportedly restored it).

ColorfulTabs changes the tab design for the worse, and exhibits rendering problems on Firefox 2.0.0.10.

HashColouredTabs+ (HCT+) works well in 2.0.0.10, leaves the native tab design alone, and is more visually unobtrusive than coloring the entire tab. I keep favicons turned off in about:config anyway to reduce bookmark file bloat, so HCT+ is a good fit. I tried HCT+ a while ago when it wasn't working so well, and ended up using ChromaTabs. I feel lucky that 2.0.0.10 broke ChromaTabs and caused me to try HCT+ again.

(Author: note that HCT+ does not appear in the search results for "color tabs" or "tab colors" at addons.mozilla.org, while ChromaTabs and ColorfulTabs do. It seems the plurals are missing from the HCT+ page search terms.)

This review is for a previous version of the add-on (0.4.14).