use script ntc.js
<script type="text/javascript">
function onBGColorPicked(sender) {
var hiddenField = document.getElementById('<%=bgColor.ClientID %>');
hiddenField.value = sender.getColor();
// alert(hiddenField.value);
var n_match = ntc.name(hiddenField.value);
//alert(n_match);
n_rgb = n_match[0]; // This is the RGB value of the closest matching color
n_name = n_match[1]; // This is the text string for the name of the match
n_exactmatch = n_match[2]; // True if exact color match, False if close-match
//alert(n_match);
document.getElementById('<%= hdncolorname.ClientID%>').value = n_match[1];
//alert(hdncolorname.value);
}
</script>