_base.scss

/**
 * The result of this file structure is ONE *.css file per theme. Making a global change 
 * to _base or _config partial will update all themes that inherit from them. #win
 */

@import 'config';

/**
 * Global
 */

body {
  background-color: $background-color;
  color: $body-copy-color;
}

_config.scss

// Colors

$background-color: #eee !default;
$body-copy-color: #222 !default;

theme01.scss

// Base overrides

$background-color: #ccc;
$body-copy-color: #111;

// Inherit from base...

@import 'base';

/**

Theme-specific CSS goes here: modules, widgets, plugins, whatever...

**/