如何为我的JTextArea的这个框架/边框着色？

import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Insets;
import javax.swing.border.Border;

public class CustomBorder implements Border {
    private Color borderColor;

    public CustomBorder(Color color) {
        this.borderColor = color;
    }

    @Override
    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
        g.setColor(borderColor);
        g.drawRect(x, y, width - 1, height - 1);
    }

    @Override
    public Insets getBorderInsets(Component c) {
        return new Insets(2, 2, 2, 2); // 设置边框的内边距
    }

    @Override
    public boolean isBorderOpaque() {
        return true;
    }
}

import javax.swing.JFrame;
import javax.swing.JTextArea;
import java.awt.Color;

public class MainFrame extends JFrame {
    public MainFrame() {
        JTextArea textArea = new JTextArea();
        textArea.setBorder(new CustomBorder(Color.RED)); // 设置边框颜色为红色
        add(textArea);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400, 300);
        setVisible(true);
    }

    public static void main(String[] args) {
        new MainFrame();
    }
}