html - CSS :first-child pseudo-element -

Why is not my code intended? The first article should have a background-colored green color how can I do without the class or the ID? I am sorry for the transcript, but my post needs more lessons to forgive me, but my post needs more lessons.

  & lt ;! DOCTYPE html & gt; & Lt; Html & gt; & Lt; Top & gt; & Lt; Meta charset = "UTF-8" & gt; & Lt; Title & gt; Stack & lt; / Title & gt; & Lt; Link rel = "stylesheet" href = "css / style_new.css" & gt; & Lt; / Head & gt; & Lt; Body & gt; & Lt; Section & gt; & Lt; H1 & gt; This is the H1 header & lt; / H1> & Lt; Articles & gt; & Lt; P & gt; Invite an advertisement for a website for advertising on this website & lt; / P & gt; & Lt; / Article & gt; & Lt; Articles & gt; & Lt; P & gt; Ready to prepare for your work, but it is not working yet, but only for working for them, they have to work just before work and work. For a small farm, & lt; / P & gt; & Lt; / Article & gt; & Lt; Articles & gt; & Lt; P & gt; Getting ready to prepare for your work, but it is not working yet, but only for working for them, they have to work just before work and work. For a small farm, & lt; / P & gt; & Lt; / Article & gt; & Lt; / Section & gt; & Lt; / Body & gt; & Lt; / Html & gt;  

CSS code:

  section article: first-child {background color: green; } Section Text: Last-Baby {background-color: red; }   
 
 
 Actually the first child of the segment tag is not  h1  Articles are Instead, use the code given below,  
  section text: first-type {background color: green; }