Let user pick background Image/Color on node form
I suggest you do it in your  node.tpl.php. You can add the style attribute directly to the attributes array in a node preprocess. 

in your template.php , load(add css file ) or insert in-line css style

function THEMENAME_preprocess_node(&amp;$variables) {
  $type = $variables['type'];
   // dpm($$variables['node']);
  // as example
 if($color=$variables['node']-&gt;field_color['und'][0]['value']){
 $css = "p {background-color: $color }";
 drupal_add_css($css, 'inline');
   }
 }


you can do something like this .I hope this solution get you some good clue .