Colours for Comments

[magnavox_23]

I have been futzing with my new layout, which is 'Gibbous' by Phidari for Heads Up.

It's looking great, the only thing I am stuck on is that I am wanting the comment box background (#ffffff) to be the same colour as the post background (#c6b6b3). Unfortunately, I cannot find an option for this in the customizer:



I can toggle it on and off in the Firefox inspector, but my knowledge beyond that is limited:


Are there any options for using some custom css to change that colour, or hide it?

Any help or advice is much appreciated! <3