用java编写编写程序，程序开始运行时在界面中显示一个白色的圆，当在圆中按下鼠标键时颜色变为蓝色，释放鼠标时颜色为红色。界面如下图所示：

可以使用Java的Swing库来实现该程序。以下是代码实现：

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class ColorfulCircle extends JPanel {
    private Color circleColor;
    private int x, y, radius;

    public ColorfulCircle() {
        circleColor = Color.WHITE;
        x = 200;
        y = 200;
        radius = 50;

        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                if (e.getX() > x - radius && e.getX() < x + radius && e.getY() > y - radius && e.getY() < y + radius) {
                    circleColor = Color.BLUE;
                }
            }

            @Override
            public void mouseReleased(MouseEvent e) {
                circleColor = Color.RED;
            }
        });
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(circleColor);
        g.fillOval(x - radius, y - radius, radius * 2, radius * 2);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Colorful Circle");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);
        frame.setLocationRelativeTo(null);
        frame.add(new ColorfulCircle());
        frame.setVisible(true);
    }
}

运行程序后，就可以看到一个白色的圆了。按下鼠标键时，圆会变为蓝色，释放鼠标时，圆会变为红色。