Set colour for lines, texts etc.

java.awt.Color
java.awt.Graphics
The example hands out a red text („Hello world!“) and a red line.

public void paintComponent(Graphics g) {
   g.setColor(Color.RED);
   // Also red: g.setColor(255, 0, 0);
   g.drawString("Hello world!", 10, 10);
   g.drawLine(g, 0, 0, 10, 10);
}