Update your Flash Player Version 18.0.0.209
https://www.adobe.com/products/flashplayer/distribution3.html Note: Windows users must download the “Internet Explorer” and “Plugin-based browsers” installers.

See if there are updates for your graphics drivers https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

Seems you missed to attach an image :) So attach please . However You can play with Firefox Content Fonts and Colors and check whether it uses the system colors (if not check the box ).

Goto Menu(Right top bar with three lines stacked) >Options>Fonts and Colors>Click on Colors . or type about:preferences#content in url bar and press Enter.

Make sure that you haven't enabled a High Contrast theme in the Windows/Mac Accessibility settings.

Make sure that you allow pages to choose their own colors.

• Tools > Options > Content : Fonts & Colors > Colors : Override the colors specified by the page with my selections above

Try "Never" if the default "Only with High Contrast themes" isn't working.

This setting affects background images.

See also:

• http://kb.mozillazine.org/Website_colors_are_wrong