Less Pull Extension by Jiri Arion

Less Pull is a free Mac menu-bar app that takes the color out of your screen, so it pulls at you less, and adds warmth when you like. Every app and every website can have its own settings.

This extension has no buttons and no settings of its own. It tells the Less Pull app which website is in front, so the app can apply the exception you set for that site: full color for a photo site, a little warmth for a reading site, and your quiet defaults everywhere else. You set website exceptions from the Less Pull menu on your Mac, not in Firefox.

What it reads: the address of the active tab in the window in front. Private windows are never reported. What it does not do: read or change anything on a page, see what you type, use the network. The address goes to the Less Pull app on the same Mac and is kept in memory only, never stored.

Requires the free Less Pull app for macOS: https://github.com/Archangeloi89/less-pull