How to: Set Font Attributes for the Windows Forms RichTextBox Control
The Windows Forms RichTextBox control has numerous options for formatting the text it displays. You can make the selected characters bold, underlined, or italic, using the SelectionFont property. You can also use this property to change the size and typeface of the selected characters. The SelectionColor property enables you to change the selected characters' color.
To change the appearance of characters
Set the SelectionColor property to an appropriate color.
richTextBox1.SelectionFont = new Font("Tahoma", 12, FontStyle.Bold); richTextBox1.SelectionColor = System.Drawing.Color.Red;
These properties only affect selected text, or, if no text is selected, the text that is typed at the current location of the insertion point. For information on selecting text programmatically, see TextBoxBase.Select Method.