So in order to change Jsbin's theme one can go to console and write
jsbin.settings.editor.theme = "theme-you-want";
as I read here.
I like monokai theme but unfortunately there is a big drawback about dark themes. When you get your cursor on a line, whole line turnes white (like marking the whole line). The problem is that text is also white and I can't see text! Does anyone else have this problem and a possible workaround?