Are you referring to upgrade from the free to pro version of the theme? If you are then, can you follow these links: https://docs.themegrill.com/knowledgebase/installing-a-wordpress-theme/ https://docs.themegrill.com/knowledgebase/how-to-upgrade-from-free-to-pro-theme/ https://docs.themegrill.com/knowledgebase/will-i-lose-my-work-if-i-update-from-free-version-to-pro-version/ and see if that helps? And if you are referring to dark skin option then, can you visit Appearance->Customize->Design Options->Skin Color section and choose the required once from there and check once? Thanks.
When i update colormag theme directly in wordpress and by update. theme will update but it causes some type of error like as Wp-vcd WordPress file is created automatically and showing viruses in function.php file and post.php.