I see you are using a beta version.

When you first open the browser, both are grayed out because there is no session history yet.

When you change to another page, you will now have a 'back' history.

You will not have a 'forward' history unless you use the 'back' button.

Are you saying the buttons are always dark?

Thanks. What I'm saying is that I can be using my browser for hours and the back/forward buttons are almost always greyed out since two updates ago now.

Let’s do a full clean re-install; Download Firefox For All languages And Systems {web link}

Save the file. Then Close Firefox.

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Do Not remove the profiles folder.

Look for, and rename any Mozilla or Firefox program folders by adding .old to them. Do not rename the Mozilla Thunderbird folder if there is one.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. If all goes well, remove the OLD folders when you are done. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode This shows how to Start all Computers in Safe Mode; Free Online Encyclopedia

Before I go ahead with the steps you've outlined, I should add that this same issue exists on both my computers starting two updates ago. One computer is Windows 10 and the other Windows 7.

There have been issues reported with the beta version on various platforms possibly caused by the redesign (Photon). I'm not sure whether these have been fixed or maybe there is another regression.

Bug 1365195 - [Photon] Implement new back button appearance Bug 1367273 - Open state of Back button is no longer indicated

• https://bugzilla.mozilla.org/buglist.cgi?query_format=specific&order=bugs.bug_id%20desc&bug_status=&chfieldto=Now&chfieldfrom=2016-01-01&content=%22back%20button%22

Thanks. Downgrading to 54.0 (non-beta) fixed the issue.