Rated 2 out of 5 stars

Great idea, I had it installed for about a week but ultimately uninstalled it, for two reasons.

First, the addon's Options menu contains no text at all. All the options are presented with pictures which are obviously less-intuitive than the developer thinks they are. I had to read through the reviews here just to figure out what they were.

Second, and much more importantly, there is no way to customize the colour used. Although I love how it uses the domain name to decide the colour, sometimes the colour chosen contrasts badly with the dominant colour theme of the website itself, and there is no way within the addon to change this.

This review is for a previous version of the add-on (0.4.21). 

Are you, perchance, still using Fx 2? The Set Icon Colour dialogue - see preview image #4 - is only available from Fx 3.