import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class MyPanel extends JPanel {
  private Color color;

  public MyPanel() {
    super();
    this.setPreferredSize(new Dimension(500,500));
  }

  public void setColor(float r, float g, float b) {
    color = new Color(r,g,b);
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.setColor(color);
    g.fillOval(500/8, 500/8, 500/2, 500/2);
  }
}