ImmutableList.Builder<Integer> webSafeColorsBuilder = ImmutableList.builder();
    for (Integer red : colorElem) {
      for (Integer green : colorElem) {
        for (Integer blue : colorElem) {
          webSafeColorsBuilder.add((red << 16) + (green << 8) + blue);
        }
      }
    }
    ImmutableList<Integer> webSafeColors = webSafeColorsBuilder.build();
    assertEquals(216, webSafeColors.size());

   * Example usage:
   *
   * <pre>{@code
   * Color red = new Color("red", 255, 0, 0);
   * ...
   * ImmutableSet<Color> allColors = ImmutableSet.of(red, green, blue);
   *
   * ImmutableMap<String, Color> colorForName =
   *     uniqueIndex(allColors, c -> c.toString());
   * assertThat(colorForName).containsEntry("red", red);
   * }</pre>
   *

   *
   * <pre>{@code
   * Color red = new Color("red", 255, 0, 0);
   * ...
   * FluentIterable<Color> allColors = FluentIterable.from(ImmutableSet.of(red, green, blue));
   *
   * Map<String, Color> colorForName = allColors.uniqueIndex(toStringFunction());
   * assertThat(colorForName).containsEntry("red", red);
   * }</pre>
   *