There is a separate css file inside the plugin folder which you can use to make any additional changes. If you want custom css for each slider then you can use the same file to write them, but you will need to use the ids of the elements accordingly.
If you use sliders on different pages then you can dequeue the current css file and load any custom css file on your header according to your pages.
Please, contact me via the contact page on my site, if you should have further queries regarding the premium version.
Hope this helps!