How to restyle button (link or input of type button) on version 1.4.2?

How to restyle button (link or input of type button) on version 1.4.2?

here is my problem, i have a link
<a data-enhanced="true" class="my-button ui-btn ui-btn-left ui-icon-back ui-btn-icon-left ui-btn-inline" data-rel="back">Back</a>

now i want to restyle it with a different background color and foreground color, so I have
.my-button      {background-color:blue !important;
                        color:red !important;
}

but somehow the "important" does not make the browser use the color i specified for my-button.
I see that the link inherits a lot of classes such as page-theme-a, etc., but i thought the "important" will make
the browser use the colors i specified. is there a way for me to force the browser use these as long as a link has a class of my-button, no matter what other classes it has?

thanks a lot in advance.