WordPress visual editor background

I was wondering if anyone could help me out?

Trying to change the color of the visual editor background and i found the css to do it but whenever I change it, it always reverts back to the white no matter what color i change it to.

From the web console on firefox i can even change it and open the css it shows loaded and it has the incorrect value.

Whatever this is:

?wp-mce-4310-20160418

Is causing my problem but I can’t figure out what it is or where it’s coming from.

You can see exactly what I mean:

https://misfithorrors.com/wp-includes/js/tinymce/skins/lightgray/content.min.css?wp-mce-4310-20160418

now delete the ?wp-mce-4310-20160418 and hit enter and you can see the correct value it should be, the very first color.

HELP!! ??