customizing "buttonTitle" font color doesn't work

[ms83]

hi,

i've got some buttons which open and close some portlet windows. now i tried to override the font color with my own css style when the button has closed the window. but it has no effect. the button's color is still the same as before.
when i try to put a border around it or something else, it works. strange...
here's the code of the button action:

action: function() {
            if (portletArray[this.pid].isVisible()) {
                this.closeWindow();
                this.setBaseStyle("GFbuttonTitle");
            }
            else {
                this.openWindow();
                this.setBaseStyle("buttonTitle");
            }
        }

a better way would be, if i could change all button images, i.e. "start", "stretch" and "end" but only the stretch image is defined in the skin styles. where are the other ones defined? couldn't find anything in the whole skin directory.

maybe anyone can help me in at least one of these problems.
thx!