Synthetica LAF JTabbedPane background color

Question

Im using Synthetica LAF for Java. Im adding JTabbedPane with JPanel as tabs. When setting JPanel.setBackground() then for some tabs it works, for some not and for others the color appears when I resize the window of my GUI application. I tried to set it from the reference like:

JPanel tab = new MyTab();
tab.setBackground(Color.red);
tabbedPane.add(null, null, tab, null);

and I tried to set inside the MyTab class itself like:

this.setBackground(Color.red);

How can I get it to work for every tab?