The style sheet object (or an array of them if you define only a pseudo element selector like :before)
GreenSock Docs (HTML5/JS)
CSSRulePlugin.getRule()
CSSRulePlugin.getRule( selector:String ) : Object
[static] Provides a simple way to find the style sheet object associated with a particular selector like ".myClass" or "#myID".
Parameters
selector: String
The name that exactly matches the selector you want to animate (like “.myClassName”).
Returns : Object

Details
Provides a simple way to find the style sheet object associated with a particular selector like ".myClass" or "#myID". You'd use this method to determine the target of your tween. For example, let's say you have CSS like this:
.myClass {And you want to tween the color of the
color:#FF0000;
}
.myClass:before {
content:"This content is before.";
color:#00FF00;
}
.myClass:before
to blue. Make sure you load the CSSRulePlugin.js file and then you can do this:var rule = CSSRulePlugin.getRule(".myClass:before"); //get the ruleOr you can feed the value directly into the tween like this:
TweenLite.to(rule, 3, {cssRule:{color:"#0000FF"}});
TweenLite.to( CSSRulePlugin.getRule(".myClass:before"), 3, {cssRule:{color:"#0000FF"}});