Java swing custom BasicButtonUI get it's buttons properties

Question

I'm new to Java, especially to swing and I was trying to make a button that has some custom property (color, number) and I wanted to make it a round button so my implementation was the following:

NumberButton testbutton = new NumberButton("0");
testbutton.setUI(new BasicButtonUI() {
    @Override
    public void update(Graphics g, JComponent c) {
        if (c.isOpaque()) {
            g.setColor(testbutton.getColor());
            g.fillRoundRect(0, 0, c.getWidth(), c.getHeight(), 100, 100);
        }
        paint(g, c);
    }
});
mainPanel.add(testbutton);

The problem is that I want to make this BasicButtonUI generally callable custom class but I don't know how can I get from inside the "void update" function the outer testbutton's color property.

The custom NumberButton:

public class NumberButton extends JButton {
    private boolean pressState;
    private int number;
    private Color color;

    public NumberButton(String title) {
        super(title);

        this.pressState = false;
        this.number = 0;
        this.color = new Color(86, 86, 86);

        this.setPreferredSize(new Dimension(100, 100));
        this.setBackground(new Color(24, 25, 27));
        this.setAlignmentY(0.5F);
        this.setOpaque(true);

        this.addActionListener(actionEvent -> this.changePressState());
    }

    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

    public Color getColor() {
        return color;
    }

    public void setColor(Color color) {
        this.color = color;
    }

    public void changePressState(){
        this.pressState = !this.pressState;
        if(this.pressState) {
            this.color = new Color(139, 239, 99, 166);
        } else {
            this.color = new Color(122, 154, 116);
        }
        this.number += 1;
        this.setText(String.valueOf(this.number));
     }
}

edit:
I tried creating a new class that extends to BasicButtonUI and the constructor takes one argument that can be set on call to the buttons color but than it doesn't changes it's color anymore:

public class RoundButtonUI extends BasicButtonUI {
    private Color color;

    RoundButtonUI(Color c) {
        super();
        this.color = c;
    }

    @Override
    public void update(Graphics g, JComponent c) {
        if (c.isOpaque()) {
            g.setColor(this.color);
            g.fillRoundRect(0, 0, c.getWidth(),c.getHeight(), 100, 100);
        }
        paint(g, c);
    }
}

and calling it like this:

NumberButton testbutton = new NumberButton("0");
testbutton.setUI(new RoundButtonUI(testbutton.getColor()));

edit #2: One thing that fixed is that in the action that is changing the color of the button I call:

public void changePressState(){
    this.pressState = !this.pressState;
    if(this.pressState) {
        this.color = new Color(139, 239, 99, 166);
    } else {
        this.color = new Color(122, 154, 116);
    }
    this.number += 1;
    this.setText(String.valueOf(this.number));
    this.setUI(new RoundButtonUI(this.color));
}

but this is not a good solution just makes a mess so please if anybody have a better solution just tell!

The full source code is upp here to check: github