Hello, Kizzume Fowler.
There are two gray themes in the browser settings - light gray (1) and dark gray (2). If they are not displayed in pure gray, but with shades of color, this indicates incorrect color reproduction of the monitor. In this case, you should either calibrate the colors using the built-in OS tools, or make color settings in the Control Panel of the graphics card. Alternatively, select the most accurate shade of gray using the tool (3) in the browser settings itself.
P.S. On my PC, shades of gray have a pure color.