A possible bug related to ColorZilla add-on

I need a small simple tool to easily "steal" the HEX code of different parts of my blog in order to better blend the new elements in it. So, recently, I have installed ColorZilla, an add-on for Firefox browser, which, according to the official description promises to: "... get a colour reading from any point in your browser, quickly adjust this colour and paste it into another program. You can Zoom the page you are viewing and measure distances between any two points on the page."

In fact, what it offers is more than I need for now, and I'm pleased with its functionality and practicability.  But, I have also noticed some annoying things going on with my Firefox browser, and I suspect it is related to this add-on because it did not happened before.

So, here is how this bug looks and behaves. On some websites, the elements of the page are surrounded (layered) by red coloured doted lines. The elements also get a pink-reddish colour. It doesn't happen with all the websites (I guess it depends of the platform), and this is why it took me some time till I realised that there is a bug lurking here. :-)

Images are always better "narrators" than words, so I post here several significant screenshots.

Bug seen on Yahoo page

Bug seen on Wikipedia page

Bug seen on Linkedin page

Bug seen on AskUbuntu page

Bug seen on Mozilla page

Ironically, I could see the bug being present even on ColorZilla's own page on Mozilla website!

Anyway, this bug is quite annoying and I intend to uninstall CollorZilla because I don't use it frequently and I don't think that it worth keeping it under these circumstances..