Hello dennis.sellers,

Would you please take a look at the Chosen Solution in this thread :

https://support.mozilla.org/en-US/questions/1201566

In addition :

https://www.intowindows.com/how-to-change-title-bar-color-in-windows-10/

Other solution

If you’ve upgraded to latest version of Firefox on Windows 10 you will notice one major difference right away; colored title bars. Firefox didn’t have a colored title bar for a good two years. The title bar of a window is supposed to be the same color as the accent color in Windows 10. Firefox’s title bar remained grey and not everyone was happy about it. The latest version finally fills this gap and this means everyone who got used to a grey title bar might not like it. Fortunately, it’s easy to disable title bar color in Firefox and get the old grey back. Disable Title Bar Color

Open Firefox and click the hamburger icon at the top right. From the menu, select ‘Customize’.

Look for the Themes dropdown on the Customize Firefox screen. Select the ‘Light’ theme and you have your grey title bar back.

The 1px line around the window in the accent color is still there.

If you want to get the colored title bar back, open the customize menu again and select the ‘Default’ theme. The col Firefox also has other themes including a nice black one. The browser doesn’t yet conform to the dark and light theme in Windows 10 however it has a nice dark theme of its own that you can select for a better browsing experience at night.