That is controlled by the stylevar control_background under the group Buttons for the tab background. For the text color that is controlled by the stylevar body_color under the group Global.
Hi Ozzy47 , thank you so much! Is it perhaps possible to somehow change it to use a custom color of my choice? For when I change the body_color for the font color, it changes in too many other places, and does not look too good. Thank you so much!