Which setting changes this?

Can't seem to find the setting to change the background color of this (the left column's, grayish color). I've searched for "color" and gone through the results, and also compared all colors I've currently changed with the color code I get using an external color picker (Pixie specifically). I've got a feeling it's there somewhere but I'm just missing it, lol.

Preferences / Display / Fields, current sort field at the top.

Aha! Thank ya, Sir!