Hi if want that look you would have to spend about 20mins reading on userChrome : *https://www.howtogeek.com/334716/how-to-customize-firefoxs-user-interface-with-userchrome.css/ If want that shape of tabs you could use this code updated a week or so ago : *https://github.com/wilfredwee/photon-australis or *http://techdows.com/2017/09/classic-theme-restorer-userchrome-css-modify-firefox-57-photon-ui.html If want more code and help can ask here or : *https://www.reddit.com/r/FirefoxCSS/ As for colour of tabs no idea, would have to ask or use this which may not work with the above : *https://addons.mozilla.org/en-GB/firefox/addon/colorfultabs/ or search yourself for aspects of thae other browser that may work for you. If want colour all over you can join here : *https://testpilot.firefox.com/ That is the best I can come up with off hand. Please let us know if this solved your issue or if need further assistance.