Change tab look for JTabbedpane

Question

How can I remove OR change colour of the border surrounding these tabs?

ALSO, is it possible to have the tab text change colour when the mouse is hovering over it?

Answer 1

Is it possible to have the tab text change colour when the mouse is hovering over it?

As stated in this answer you can set a custom component for rendering the tab title, through JTabbedPane.setTabComponentAt(int index, Component component) method. So you can do something like this:

final JTabbedPane tabbedPane = new JTabbedPane();

MouseListener mouseListener = new MouseAdapter() {            
    Color defaultColor;

    @Override
    public void mouseEntered(MouseEvent e) {
        JLabel label = (JLabel)e.getSource();
        defaultColor = label.getForeground();
        label.setForeground(Color.BLUE);
    }

    @Override
    public void mouseExited(MouseEvent e) {
        JLabel label = (JLabel)e.getSource();
        label.setForeground(defaultColor);
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        JLabel label = (JLabel)e.getSource();
        Point point = SwingUtilities.convertPoint(label, e.getPoint(), tabbedPane);
        int selectedTab = tabbedPane.getUI().tabForCoordinate(tabbedPane, point.x, point.y);
        switch(e.getButton()){
            case MouseEvent.BUTTON2: tabbedPane.removeTabAt(selectedTab); break;
                default: tabbedPane.setSelectedIndex(selectedTab);
        }                
    }

};

JLabel tab1 = new JLabel("Tab1");
tab1.addMouseListener(mouseListener);    

tabbedPane.addTab(null, new JPanel());
tabbedPane.setTabComponentAt(0, tab1);

How can I remove OR change colour of the border surrounding these tabs?

It's up to the Look and Feel decide the border color in this case. You should look into the L&F default properties and see if it's allowed change this color. For instance you could execute the following code to see L&F default properties (of course after setting the L&F):

for(Object key : UIManager.getLookAndFeelDefaults().keySet()){
    System.out.println(key + " = " + UIManager.get(key));
}