Vim background preference

I've noticed in several Vim dark color schemes that the background on lines where the user has inputed text appears one color, while blank lines below the entered text appears in a different color. One example of this is in the asu1dark color scheme. I would lik开发者_StackOverflow社区e to add this customization to my own color scheme. Does anyone know how to turn on this difference in background color? Thanks in advance for the help!

You just need to set the color for elements of type NonText. See :hi.