Update Background Color with Bootstrap 4

To make a set background color slightly lighter (or darker) make these changes to _background.scss file in utilities folder of the Bootstrap 4 source folder:

@include bg-variant('.bg-inverse', $brand-inverse);
Duplicate and modify:
@include bg-variant('.bg-inverse-lighter', lighten($brand-inverse, 10%));

Process the .scss file and use this new class (in this case bg-inverse-lighter) for the element’s background.