Change jQuery mobile icon background color dynamically

Is there a way to dynamically change the icon's background color ? I know how to change it permanently:

ui-icon-location:after{background-color: red;}

The thing is that I would like to change the background to red only when I'm a certain distance from a location using Cordova's watchPosition. By defaul the icon's background would be

.ui-icon-location:after{background-color: #3399FF;}

Everything works just fine, the icon is the only thing I would love to get working. I would appreciate any ideas.

Thanks!