This is the similar case from here https://support.mozilla.org/en-US/questions/982299?esab=a&as=aaq I wish I could attach my screenshot. Personas colors the theme to the title bar, bookmarks bar but does not color the add-on bar. I traced that adblock plus add-on blocks this page load. I disabled it and worked. I tried disabling the addon for mozilla.addons site as well as getpersonas.com but didn't work. Another strange thing is that when I reselect the theme from the icon at the addon bar, it gets applied but gives a blank (Not exactly blank but a red color background if the personas main theme is built around red. I think i've made my case clear.) What sites should I whitelist for adblock plus(tried two of the above) so that it loads or is it a problem elsewhere?