Change content color based on Date Range
In your theme, you can implement hook_preprocess_page(&amp;$variables) were you can retrieve the currently displayed content (if any) as $variables['node']. From there, you can retrieve the value of a date field using field_get_items() and use that value to assign classes to the &lt;body&gt; of the page in $variables['classes_array'].

function THEME_preprocess_page(&amp;$variables) {
  if (($node = $variables['node']) &amp;&amp; ($node-&gt;type == 'report')) {
    if ($items = field_get_items('node', $node, 'field_report_date')) {
      $variables['classes_array'][] = drupal_clean_css_identifier('report-month-' . format_date($items[0], 'custom', 'F'));
    }
  }
}