Can Elixir version be run only on production?

Well yeah you could overwrite the defaults i guess. here https://github.com/laravel/elixir/blob/master/index.js#L7 it includes a elixir.json file to load in the config. and in https://github.com/laravel/elixir/blob/master/Config.js#L6 it sets the config value as a default. So you should be able to create a elixir.json file with:

{
    "production" : true,
}

You can do this quite easily by checking mix.production

if (mix.production) {
        mix.version([
            'public/assets/css/screen.css'
        ]);
    }

Thanks to @deshiknaves for his answer. Although I couldn't get it to work it did help me in finding a similar alternative which does appear to be working as expected:

in your gulpfile.js wrap anything you want to run ONLY to run in production mode with:

elixir(function (mix) {
    // ... the rest of your gulpfile config

    if (elixir.config.production) {
        mix.version([
            'js/main.js',
            'css/main.css'
        ]);
    } else {
        // Anything you only want to run in non-production mode, e.g. BrowserSync
        mix.browserSync(); 
   }
}