How do I add a region to the Color module?
You need to also provide a color for the field you added. In fact, the function that adds the form elements for the color settings contains the following code. (See color_scheme_form().)

 foreach ($palette as $name =&gt; $value) {
    if (isset($names[$name])) {
      $form['palette'][$name] = array(
        '#type' =&gt; 'textfield',
        '#title' =&gt; $names[$name],
        '#value_callback' =&gt; 'color_palette_color_value',
        '#default_value' =&gt; $value,
        '#size' =&gt; 8,
        '#attributes' =&gt; array('dir' =&gt; LanguageInterface::DIRECTION_LTR),
      );
    }
  }


Without a color value for your field, $form['palette'][$name] will not be added, and it will not be possible to change the color for it.

In fact, the Bartik theme uses the following values, for its default palette.

$info['schemes']['default'] = array(
  'title' =&gt; t('Blue Lagoon (default)'),
  'colors' =&gt; array(
    'top' =&gt; '#055a8e',
    'bottom' =&gt; '#1d84c3',
    'bg' =&gt; '#ffffff',
    'sidebar' =&gt; '#f6f6f2',
    'sidebarborders' =&gt; '#f9f9f9',
    'footer' =&gt; '#292929',
    'titleslogan' =&gt; '#fffeff',
    'text' =&gt; '#3b3b3b',
    'link' =&gt; '#0071B3',
  ),
);


The keys you find in (for example) $info['schemes']['default']['colors'] are the same keys you find in $info['fields'].