// Set the text color and font

richTextBox1.SelectionColor = Color.Red;

richTextBox1.SelectionFont = new Font("Arial", 12, FontStyle.Bold);

​

// Append text to the control with the specified color and font

richTextBox1.AppendText("This text is bold and red!");

​

// Set the text color and font back to the default values

richTextBox1.SelectionColor = richTextBox1.ForeColor;

richTextBox1.SelectionFont = richTextBox1.Font;

​

// Set the text color to blue

richTextBox1.SelectionColor = Color.Blue;

​

// Append text to the control with the specified color

richTextBox1.AppendText("Hello, world!");

​

// Set the text color back to the default color

richTextBox1.SelectionColor = richTextBox1.ForeColor;

​