It sort of sounds like a scaling issue. You possible can do that with your video card.

Is Windows Taskbar in the proper position.? Meaning look in the right bottom corner. The bar there that drops everything down when all folders and stuff is open on the desktop. Can you see all of it or just a tiny sliver or not at all ? If tiny or not at all try video card and scaling so can see more of it. There is scaling in Windows but not very useful. Could give that a try then Firefox would possibly go to the edges.

If not running 57.02 please update : https://support.mozilla.org/en-US/kb/update-firefox-latest-version

Flash 27.0 r0 Please update Flash Player Version: 28.0.0.126 Current Version | 3 days ago https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, . . . .) Note: Other software is offered in the download. <Windows Only>

Please let us know if this solved your issue or if need further assistance.

Everything is scaling as it should be. To clarify, Firefox does go to the edges when I am in full screen mode. It is just when I am not in full screen mode the colored border comes up.

Please : https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer and https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles then https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings TEST.......

If still not fixed the issue maybe in your profile : Make a new one and test ...: https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles TEST.........

Please let us know if this solved your issue or if need further assistance.