Modify background of a button onclick event

hi everybody,

I have a problem with the theme blue crystal and the element button.

When i press the button it change the background of the button to blue, only when do the action, after y have a button.setclass("x") so it just mudify the colour when do the action.

anyone knows how hide this effect? i try with that

#button:active {

    vertical-align: top;

    padding: 8px 13px 6px;

    background-color:black !important;

}

thanks