Now on Windows 10. All my drop down boxes have become a gray color in an old style. What? How can I correct this?

[WPCentral Question]

Now on Windows 10. All my drop down boxes have become a gray colour in an old style.

I'm using Firefox, and have managed to change the style to a blue colour using a Theme. However, all my drop down menus are a boring gray colour. Even Google Earth is a boring gray colour. I HATE GRAY!!!!!!!