Ok so I added an addon that would make youtube “dark” but I dontknow which one and cant find it…Im unable to remove or diable any themes or add on that would fix it
Generally speaking the “Themes” section of the Add-ons page refers to changing Firefox’s toolbar area. You probably need to check the “Extensions” section of the page.
If you have Stylus, Stylish, reStyle, xStyle, or similar user style manager, then look for its toolbar button to see whether the theme is listed there, or use its “Manage” button to look for it that way.
You can see what extensions and themes you currently have installed by navigating to about:addons in your browser. From there, you can disable the extension or theme that makes Youtube “dark.” 