title: Can't select some Facebook classes with jQuery (Chrome Extension)
body: <p>Long story short.</p>
  
  <p>If I use a CSS content_script with the following code...</p>
  
  <pre><code>._o46._nd_ ._hh7 {
  background-color:#333!important;}
  </code></pre>
  
  <p>...it works. <strong><em>It changes the Facebook Messenger message bubble color to #333.</em></strong></p>
  
  <p>But I need to do it with JS, so I'm trying to do the following with a JS content_script:</p>
  
  <pre><code>$("._o46._nd_._hh7").css("background-color", "#333")
  </code></pre>
  
  <p>But, yeah, it doesn't work for some reason I'm not aware of.</p>
  
  <p>JQuery is included, and it's working because I can change the body color from the Facebook page with it. It seems like it's Facebook Messenger specific. </p>
  
  <p>I tried modifying the selector to all possible ways. I even tried to select only the <strong>._hh7</strong> class (to change all message bubbles, not only the sender's) to see if it works but it still doesn't do the job.</p>
  
  <p>I have no clue what am I doing wrong or if I am doing something wrong at all. I'm new to Chrome Extensions, but the fact that I can change the body color with no problem makes me wonder WHAT</p>