More sidebars?

Hello, I made a post with many questions, but really, this is the most important I have: is there not a way to create more sidebars? I really like the way your widgets look when using a sidebar, but for some reason, when I create new sidebars with a plugin, it doesn’t have the same look. One thing that is odd is that they don’t all have the white background. Any ideas on these two things?