CSS

sass darken

darken($color, $amount)

//darken(#FFF, 30%)

SCSS lighten

lighten($color, $amount)
//Makes a color 
lighter.darken($color, $amount)
//Makes a color darker.

darken scss

$btn-bkg: purple;
.btn {
  display: inline-block;
  padding: 18px;
  background: $btn-bkg;
  color: white;
  &:hover {
    background: darken($btn-bkg, 10%)
  }
}

scss darken

darken($color, $amount)

scss darken color

darken($color, 5%);

SCSS lighten

saturate($color, $amount)
//Makes a color more 
saturated.desaturate($color, $amount)
//Makes a color less saturated.

scss darked color

$linkcolour: #0000FF;

a {
  color: $linkcolour;
}

a.lighter {
  color: lighten($linkcolour, 50%);
}