Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="grayscale">test2</div>

SassMeister-input.scss

// ----
// Sass (v3.3.0.rc.1)
// Compass (v0.13.alpha.10)
// ----

@mixin grayscale_element($value) {
    -webkit-filter: #{"grayscale(#{$value})"};
    -moz-filter: #{"grayscale(#{$value})"};
    filter:#{"grayscale(#{$value})"};
}

$value: 70%;

.grayscale {
    width: 100px;
    height: 100px;
    background-color: #e86ea4;
    @include grayscale_element(#{$value});
    &:hover {
        @include grayscale_element(0);
    }
}

SassMeister-output.css

.grayscale {
  width: 100px;
  height: 100px;
  background-color: #e86ea4;
  -webkit-filter: grayscale(70%);
  -moz-filter: grayscale(70%);
  filter: grayscale(70%);
}
.grayscale:hover {
  -webkit-filter: grayscale(0);
  -moz-filter: grayscale(0);
  filter: grayscale(0);
}

SassMeister-rendered.html

<div class="grayscale">test2</div>