You can check the default color settings. *Options/Preferences -> General: Fonts & Colors -> Colors ---- You can try these steps in case of issues with web pages: You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files. *hold down the Shift key and left-click the Reload button *press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux) *press "Command + Shift + R" (Mac) Clear the Cache and remove the Cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences). "Remove the Cookies" from websites that cause problems: *Options/Preferences -> Privacy & Security<br>Cookies and Site Data -> Manage Data "Clear the Cache": *Options/Preferences -> Privacy & Security<br>Cookies and Site Data -> Clear Data -> Cached Web Content: Clear If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (Adblock Plus, NoScript, Disconnect, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block content. *make sure your extensions and filters are updated to the latest version *https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems Firefox shows the shield icon at the left end of the location/address bar in case Content Blocking is blocking content. *click the shield icon for more detail and possibly disable the protection You can check the Web Console about what content is blocked *"3-bar" menu button or Tools -> Web Developer *https://support.mozilla.org/en-US/kb/tracking-protection *https://support.mozilla.org/en-US/kb/content-blocking