Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

$themes: (
  red: (
    background: red,
    color: white
  ),
  blue: (
    background: blue,
    color: green
  ),
	black: (
    background: black,
    color: yellow
  )
) !default;

@each $theme, $styles in $themes {
    .theme--#{$theme} .sidebar {
        background: map-get(map-get($themes, $theme), background);
        color: map-get(map-get($themes, $theme), color);
    }
}

SassMeister-output.css

.theme--red .sidebar {
  background: red;
  color: white;
}

.theme--blue .sidebar {
  background: blue;
  color: green;
}

.theme--black .sidebar {
  background: black;
  color: yellow;
}