You can easily use JQuery to change the CSS of HTML tags. Of course, you can either change them inside a function, or outside a function, inside the Script Tag.

Here’s a way inside an ‘onblur’ function:

$("#MyTextBox).blur(function () {
 $(this).css("background-color", "red");
}

All you’d need to do inside a Script Tag (which would make it change the color once the page loaded) would be to use the code like this:

 $(#MyTextBox).css("background-color", "red");

Though, it would probably be best to do it inside a JQuery Document Ready function.