Change Color Background on mainnav li

My customer wants main menu a background color. I have created a childtheme and inserted this text on childTheme style.css

    #mainnav ul li {
    background-color: # 3838388a

unfortunately, nothing changes on the side!
here the link

I can not find the mistake!

Hello there,

Try this code:

    #mainnav > li > a {
      background-color: #fff000;
      color: #ff0000;
      padding-left: 7px;
      padding-right: 7px;


Thank you! Works perfect! Great

You’re welcome!

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