Set color of text in a Textbox/Label to Red and make it bold in asp.net C#

TextBox1.ForeColor = Color.Red;
TextBox1.Font.Bold = True;

---

Or this can be done using a CssClass (recommended):

.highlight
{
  color:red;
  font-weight:bold;
}

TextBox1.CssClass = "highlight";

---

Or the styles can be added inline:

TextBox1.Attributes["style"] = "color:red; font-weight:bold;";

Try using the property ForeColor. Like this :

TextBox1.ForeColor = Color.Red;