THE BROWSER WINDOW HAS LIGHTER SCREEN AND BARS DARKER CAN I CHANGE THAT OR HAVE FULL CONTROL OVER THE COLOR WITHOUT DISTORTING OTHER WEBSITE

i want to customize the appearance of zen browser and i want to make a dark transparent blurred theme but the browser background is lighter than the toolbar.

i tried userchrome.css it changes the background of website causing issue in reading

i use stylus to edit certain websites and it makes the background to be transparent

is there a way to edit the background of the zenbrowser without effecting other website and full control over the colors