Changing spinner CSS

Hi,

Is there any documentation on changing the spinner CSS or behaviour?
It is currently a blue colored icon spinning in top left and I would need to change it to white and to be in the center of the page to look better.

The only thing referencing this I could find was in qsm-quiz.js file on line 903:
$container.append('<div class="qsm-spinner-loader"></div>');

But there’s no CSS anywhere relating to this or nothing and it loads so quickly I can’t check it with inspect element tool in my browser.