[jQuery] retrieving textnode?

Hi, I'm new to jQuery, finding feet.

I want to be able to say, "if the text node of a certain child
consists of certain string, do this with its css".

Gotten as far as changing the css of all the children, thus:

$(document).ready(function(){
 $("div > p::nth-child(6).css("color", "red");
  });

but

$(document).ready(function(){
 $("div > p::nth-child(6).textNode("_ _").css("color", "red");
  });
doesn't do it. Nor does textNode=...

Second question,  Firefox error console isn't muchhelp in interpreting
the error. Any suggestion for debugging?