How do I animate a background color to transparent in jQuery?

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Transparent isn’t really a color. So, you can’t animate to it. You might be able to achieve the effect you’re looking for by using a separate element for the background, and animating the opacity though.

Example:

HTML:

<body style="background-color:yellow">
  <!-- by default, "see through" to parent's background color -->
  <div id="container"> 
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
    Aenean nec magna. Nulla eu mi sit amet nibh pellentesque vehicula. 
    Vivamus congue purus non purus. Nam cursus mollis lorem.    
  </div>
</body>

Script:

// on load...
$(function()
{
  var container = $("#container");
  container
    .hover(
      // fade background div out when cursor enters, 
      function() 
      { 
        $(".background", this).stop().animate({opacity:0}); 
      }, 
      // fade back in when cursor leaves
      function() 
      { 
        $(".background", this).stop().animate({opacity:1}) 
      })
    // allow positioning child div relative to parent
    .css('position', 'relative')
    // create and append background div 
    // (initially visible, obscuring parent's background)
    .append( $("<div>")
      .attr('class', 'background')
      .css({
        backgroundColor:'blue',
        position: 'absolute',
        top:0,
        left:0,
        zIndex:-1,
        width:container.width(), 
        height:container.height()
      }) 
    );
});

Kingjeffrey’s comment points out that this answer is somewhat outdated – browsers do now support RGBA color values, so you can animate just the background. However, jQuery doesn’t support this in core – you’ll need a plugin. See also: jQuery + RGBA color animations

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