how to add multiple style values in attribute in drupal form
You can nest the style attributes as follows :

$form['precio'] = array(
  '#type' =&gt; 'textfield',
  '#title' =&gt; t('Price'),
  '#default_value' =&gt; $precio,
  '#size' =&gt; 20,
  '#attributes' =&gt; array(
    'style'=&gt;'background: none repeat scroll 0 0 #EAEAEA;
              margin: 0 3 4;
              color:red;'
  ),
  '#description' =&gt; t('Change the price'),
);