<%@ Import Namespace="System.Drawing" %>
<!DOCTYPE html>
<html>
<head>
<script runat="server">
Sub ChangeBorderColor(obj As Object, e As EventArgs)
button1.BorderColor = Color.FromName("Red")
End Sub
</script>
</head>
<body>
<form runat="server">
<asp:Button id="button1" runat="server" BorderColor="#FFCC80" BorderWidth="10px" Text="Change" OnClick="ChangeBorderColor" />
</form>
</body>
</html>