Dynamically switch file in get_template_directory_uri() | Function [closed]

If you are sure that $redux_demo["color_scheme"] is getting the corresponding value, so your code should be:

global $redux_demo;
wp_enqueue_style( 'javapaper-lightbox-style', get_template_directory_uri() . "/css/{$redux_demo['color_scheme']}.css" );

Assuming that you have files in this structure css/dark.css and css/light.css.