How to change the Brightness of a Canvas Group's Background

What I’m trying to do & what I’ve tried

I’ want to make it so that one of the color options on the canvas makes the background image of a group darker,
I’ve managed to achieve that but unfortunetly I don’t know what to write for this to only affect the group’s background

.mod-canvas-color-2 {
        .canvas-node-container {filter: brightness(30%);}


I’ve looked at Obsidian Help and it seems there’s not much there that can help me with this. I tried writing it like this but it doesn’t work

     .canvas-node-container[data-type="group"] {filter: brightness(30%);}

Looking at the developer console I think I should be writing (or replacing) this into my snippet: .canvas-node canvas-node-group but I just don’t know how to properly write it.