How to change background color of the editor groups in Visual Studio Code?

I am trying to make some changes to the default Dark Visual Studio Code
Theme. I like the Visual Studio Code dark default theme and its color, but I
just need it to be more dark or black… now I almost succeed… but I
cannot seem to find the property to change the editor group background
color.

What is the name of the property to change the background color of the marked area in red of the picture

>Solution :

It is called editorGroupHeader.tabsBackground:

{
  "workbench.colorCustomizations": {
    "[Default Dark+]": {
      "editorGroupHeader.tabsBackground": "#ff0000"
    }
  }
}