Fantatsic! Rated 5 out of 5 stars
Great work on creating this.
I used use a custom user style bookmarklet (generator by Jesse Ruderman) to quickly change page colors but for some reason, it stop working. Could be an extension conflict but your add-on works great and provides quick customization options.
I'd love to see a toolbar button perhaps with a drop down to access the other color options mostly for the fact that this add-on will be very useful for persons with visual impairments and so accessing your add-on through a toolbar button would be easier.
All in all, it's an awesome add-on. I sincerely appreciate your effort and time that you put into it.
I'm working on it.