How to change color of GridLayout spacing?

Question

the GridLayout new GridLayout(5, 8, 4, 4) is shown as a card in a CardLayout. I color the squares bluish by setting the background color of all JPanels I insert into the gridlayout. Where should I look to change the color of the white outlines(the 4 pixel horizontal and vertical spacing I've specified)?

Answer 1

The layout itself has no color, it's merely in charge of calculating and setting the positions and sizes of the components inside the container it is assigned to.

What you need to do it to set the background of that container, ie the container to which you set the layout

someContainer.setLayout(new GridLayout(...));
someContainer.setBackground(new Color(...));