1、新建静态扩展方法public static class RichTextBoxExtension{public static void AppendTextColorful(this RichTextBox rtBox, string text, Color color, bool addNewLine = true){if (addNewLine){text += Environment.NewLine;}rtBox.SelectionStart = rtBox.TextLength;rtBox.SelectionLength = 0;rtBox.SelectionColor = color;rtBox.AppendText(text);rtBox.SelectionColor = rtBox.ForeColor;}}2、调用
this.richTextBox.AppendTextColorful(msg, color);