It’s pretty common to need a bit of transparent black or white. In CSS, you can do:
.half-black {
background: rgba(0, 0, 0, 0.5);
}
It gets easier in Sass, where you can substitute a color name:
.half-black {
background: rgba(black, 0.5);
}
Or make it easier still, by making custom functions:
@function black($opacity) {
@return rgba(black, $opacity)
}
@function white($opacity) {
@return rgba(white, $opacity)
}
.half-black {
background: black(0.5);
}