Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.0.rc.2)
// Compass (v1.0.0.alpha.17)
// ----

@mixin themify($element, $property, $color-light: false) {
    $pages: ();
    @if $color-light == "true" {
        $pages: home forestGreen, about darkOrange, work dodgerBlue, contact fireBrick;
    }
    @else {
        $pages: home darkGreen, about orange, work royalBlue, contact crimson;
    }
    @each $page in $pages {
        .page--#{nth($page, 1)} .#{$element} {
            #{$property}: nth($page, 2);
        }
    }
}

/* Call the mixin */
@include themify(site-nav, background-color, $color-light: true);

SassMeister-output.css

/* Call the mixin */
.page--home .site-nav {
  background-color: darkgreen;
}

.page--about .site-nav {
  background-color: orange;
}

.page--work .site-nav {
  background-color: royalblue;
}

.page--contact .site-nav {
  background-color: crimson;
}