hoe to change color of text in text box while entering data

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C#

ASP.NET

I am working with asp.net c#.
I have a text box for entering user name .

What i need is when the page load , this text box should carry the data 'username ' in ash colour and when user click on the text box the 'username' text should disappear .

when user types anything inside , the color of text should change to black from ash.

I used the below code. but color how to change?

<asp:TextBox ID="txtContact" runat="server" ForeColor="#999999"  value="Contact Number" onfocus="if (this.value == 'Contact Number')  {this.value = '';}"
                     onblur="if(this.value == '') { this.value='Contact Number';}"
                        Width="251px"></asp:TextBox>