I was listening to the ShopTalk Show a little while ago and they had Adam Argyle on talking about VisBug. It's a browser extension that is almost like Dev Tools for designers. I like the accessibility features that it has but it has a lot of other tools. Such as allowing you to update colors and move elements around the page without having to use the inspector. I think this is a good tool for designers who are not comfortable pushing HTML/CSS around but wants to be able to work with the actual site.
Checkout visbug.web.app for more details to see how it works. You can (download for Chrome) now but the Firefox extension is coming soon.