Javascript, adding an removing CSS on button press (shutter reloaded)

I've tried editing the Shutter Reloaded script to simply add in a bit of CSS when the resize button is pressed, but I can't get it to work as my javascript knowledge is terrible. This is what I've tied doing:

  Resize : function(ln) {
             if ( this.resizing ) return;
             if ( ! this.I('shShutter') ) return;
             var W = this.I('shWrap');
             if ( W ) W.style.visibility = 'hidden';
    window.setTimeout(function(){shutterReloaded.resizing = null},500);
    window.setTimeout(new Function('shutterReloaded.VP = null;shutterReloaded.Make("'+ln+'");'),100);
    this.resizing = true;
    document.getElementById("colour").style.property=display="none";
    },

I'm wanting to add: display: "none"; to the div #colour, but yeah can't seem to get it to work.

The page its on is this: Link

It probably helps to have the rest of the code too:

shutter.js

Any idea's guys?

You're almost there, try this:

document.getElementById("colour").style.display="none";