is there any general or universal way to change Drupal's objects CSS?
No. Of course there are default Drupal styles but there are no guarantees that whichever base theme you are working from hasn't overridden them.

The good news is that most popular base themes will implement classes that are universal to a particular type of output, like a row or a block. For instance, Foundation uses its own 'row' and 'column' but retains the core 'block' class.

Since you asked :), here is something you might do to add padding to columns in a Bootstrap subtheme:

.main-container &gt; .row &gt; section {padding: 1em;}


Note the '>' combinator. This refers to immediate descendents. 

&lt;div class="main-container"&gt;
  &lt;div class="row"&gt;
    &lt;section&gt;
      &lt;!-- this element will be our target since it's an immediate descendent of .row --&gt;
      &lt;section&gt;
        &lt;!-- this element is not --&gt;
      &lt;/section&gt;
    &lt;/section&gt;
  &lt;/div&gt;
&lt;/div&gt;


Note: If a selector is prefixed with '#' it is an id, and will only apply to one element. A class is prefixed with '.' and can apply to multiple elements. So all rows in bootstrap can be accessed with:

.row {padding: 1em;}