Toggle Website Colors (Tab) от Manuel Reimer

This addon adds a checkbox to the page context menu and a button in the address bar to toggle the website colors, set by the author. This is meant to be used on pages with, for example, orange text on yellow background. In this case, just disable website colors and comfortably read black on white text.

Other features, possible with this addon:

• Automatically disable colors for all new tabs (disabled by default)
• Freely customizable colors to be used

The addon always works "per tab". So if you disable website colors in one tab, all the other tabs are unchanged.