Hi there,
The blog page is the WordPress default posts page so it cannot be edited normally like a static page – it simply displays all the posts you’ve added.
It cannot be edited using Elementor:
https://docs.elementor.com/article/56-content-area-not-found
But GP has some options for it:
https://docs.generatepress.com/article/blog-content-layout/
As for the difference in colors, go to Customizer > Additional CSS and remove this block of CSS:
/* Blog */
.blog {
background-color: #323232;
}
.blog #masthead {
background-color: #000;
}
.blog .post {
border-bottom: 2px solid rgba(255,255,255,0.2);
}
Let me know if this helps 🙂