Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.12)
// Compass (v1.0.3)
// ----

// per ogni tema dichiaro la palette
$themes: (
    theme1: (
        base-color: red
    ),
    theme2: (
        base-color: blue
    )
);

@mixin skin($property, $color) {

    @each $key, $value in $themes {
        
        @if map-get($value, $color) != null {
        
            .t-#{$key} & {
                #{$property}: map-get($value, $color);
            }
            
        } @else {
            @warn('color is missing from theme');
        }
    }

}

// applico i colori del tema all elemento
a {
    @include skin(color, base-color);
}

SassMeister-output.css

.t-theme1 a {
  color: red;
}
.t-theme2 a {
  color: blue;
}