Hey @Heemin thanks for your reply. I am gonna try it, just one more question that I am confused about is that… how am I gonna target certain category page? this CSS file will be loaded for all the pages.
Now how will I want to display class .category-page-men to be displayed under the Mega Menu of category page Men.
Also, about putting CSS in pub, you mean then in the web/css directory I need to put src as http://www.magento2-website.com/custom.css ???