How to change background color of blog posts using Vortex theme

I’m using the Vortex theme for my website and I uploaded a background image using the Fullscreen BG Image plug-in! My issue is the background for all the blog posts are transparent. You can’t read the text on any of the posts due to the background showing through! Is there a code I can use with the color # that I want to background to be so that it will show up? I’ve googled it a few time and it only shows me how to change the color of the headers on blog post but nothing about how to change the actual background color of the post. If anyone knows how to fix this please let me know! I would really appreciate it.