// define your colors
$colors: (
  'pink': #E2127A,
  'brand-primary': 'pink',
  'site-background': 'brand-primary',
);

// color function
@function color($color) {
  // our conditional statement
  @if map-get($colors, $color) {
    // follow the path one step
    $new-color: map-get($colors, $color);
    // recursion!
    $color: color($new-color);
  }
  
  @return $color;
}

// use your new function!
body {
  background: color('site-background');
}



// other styles...
body {  
  font-size: 8vmin;
  font-family: monospace;
  text-align: center;
  padding: 40vmin 2em;

  &::after {
    content: "‘site-background’ == #{color('site-background')}";
  }
}