var redbtnstyle = load("res://Themes/Button/RedButton.tres")
"RedButton.tres" is a theme file I created by saving my custom theme in the editor. I'm loading it into a variable and that variable should be used to override my button style.
But I can't load the theme file in through code, it says that the style is empty, but it does work when I do it with the editor/inspector...
Example project (godot 2)