如何通过使用jQuery单击前面的段落编号来更改相应段落的背景颜色？

I have 6 paragraphs as follows:

我有6个段落如下:

<div id="col2">

<p class="firstparagraph"> firstparagraph </p>
<p class="secondparagraph"> secondparagraph </p>
<p class="thirdparagraph">  thirdparagrap  </p>
<p class="fourthparagraph"> fourthparagraph </p>
<p class="fifthparagraph">  fifthparagraph  </p>
<p class="sixthparagraph">  sixthparagraph  </p>
</div> 
<