There are three main color settings. Theme colors, cover template colors and individual block colors.
Post with Excerpt and Featured Image

This is a post that has an excerpt and a featured image. Pages can not have excerpts (this text is the excerpt). But pages can have featured images.
Twenty Twenty theme has two widget areas Footer #1 and Footer #2
Default Post With Excerpt
This is the post excerpt. Pages do not have this option.
Example Blocks
Blocks give you many more layout options than the classic editor. And in the Twenty Twenty theme, blocks look great.
The Full Width Template
The full width template is made for page builders If you use a page builder such as Beaver Builder or Elementor, the full width page template is just what you need. If you’re not using Beaver Builder or Elementor, you probably won’t use the full width template. The Full Width Template This is a full […]
Because this is a post I can add an Excerpt here. Pages do not have Excerpts.

This is the default template WITH a featured image. The featured image straddles the border between the header section and the post content section. This is more obvious if you have a dark header background.
Post Cover Template

This is an excerpt and it displays below the post title on posts that use the Cover Template. Pages do not have an excerpt option.
At first the color settings are confusing. But they make real sense when you understand how they work.