change background color to black

[gobimahato]

I want to change background color to pure dark from purple default bg color

[skbolton]

After you set the colorscheme to embark you can manually adjust highlight groups to whatever you want.

Background is controlled by Normal but you'll probably then need to adjust the gutters and popup windows too. Those are things like LineNr, CursorLineNr, SignColumn, FoldColumn, Pmenu*.