Image Background Color Picker от Marnes

This addon won't be maintained further. I'm shelving this project due to lack of interest/utility and too much burden. The addon will remain available for download as long as the store allows, and the source on gitlab will also remain available to fork.
I do have a greasyfork account you can check out, and you can get new versions of CSL, DID, and IBCP there!

Available for Chrome too.

Functionality
You can select any color or the checkerboard option, and it will be applied to all direct image view tabs.

The Options screen will automatically open after add-on updates if they force a change to any of your settings.

Please rate/review/donate! :)
A lot of time and work goes into creating my addons, and making changes or troubleshooting issues for users.

Problem, bug, broken, question, request?
Per Mozilla policy, only an evaluation of an addon's entire function with reasonable expectations is a proper review. Vague complaints or 1-star ratings for single reasons are considered spam, as are false claims about the addon not working at all. For more detailed discussions, use the linked support site or email.