Hello Dkeoki-
Thanks for reaching out, and thanks for using the Post and Page Builder for WordPress.
The colors of the Post List widget are controlled with the site’s color palette, in Customize > Color Palette.
Design controls, like number of columns, and controls to show or hide various elements are in the Widget’s menu itself. Click on the Post List, and look for the Edit (Pencil) icon above it.
Beyond those controls, you can further customize your post list with Custom CSS. If you can describe what you’re looking to accomplish, we’ll be happy to help provide you with some CSS rules to do it.