Create a function in mixins.

gistfile1.css

// Mixins
@mixin gradient($color) {
  background: -webkit-linear-gradient(top, $color 0%,$color 100%);
  background: -o-linear-gradient(top, $color 0%,$color 100%);
  background: -ms-linear-gradient(top, $color 0%,$color 100%);
  background: linear-gradient(top, $color 0%,$color 100%);
  background: -moz-linear-gradient(top, $color 0%,$color 100%);
}