Code:
.appWindow window1 {
     background-color: Green;
}
I'm not sure what this is trying to do - this might be again a question of knowing CSS. Here's what the first line means in CSS:

"Select all items with tag name 'window1' inside any element with class 'appWindow', and apply these styles..."

However, there is no such thing as a html tag 'window1', so this query will do nothing.

The reason my query worked is that there *is* a tag named textarea - that is how you render a multi-line text input. The query finds all textarea tags anywhere inside any tag with class "newData".

My suggestion was to actually change the class names on the element that is the body of the window - calling getBody() should get a reference to the element that is the body of the window. Adding a classname to that directly *should* allow you to style it, but there are other considerations - existing styles (your selector must be 'stronger', i.e. more specific), other widgets added that set their own backgrounds (the color might be inherited, or bleeding through, and the child widget is the problem in one theme vs another), etc. Knowing more about the widgets you have set up and how you've set the styles will make it easier to help. Learning CSS will help too - I can't explain that in a forum post unfortunately.