SassColorTest.scss

// Variable definition
$base-color: #c6538c;
// Variable definition and reference
$border-dark: rgba($base-color, 0.88);

.alert {
    // Variable reference
    border: 1px solid $border-dark;
}

// Mixin declaration
@mixin reset-list {
    margin: 0;
    padding: 0;
    list-style: none;
}

// Mixin declaration
@mixin horizontal-list {
    // Mixin reference
    @include reset-list;

    li {
        display: inline-block;

        margin: {
            left: -2px;
            right: 2em;
        }
    }
}

nav ul {
    // Mixin reference
    @include horizontal-list;
}