On the definition of the aio-orange button in the all-in-one-buttons/css/display.css?ver=4.1.1 add !important after the #FFF.
The color is overwritten because you load the AIO styles first and later some other style that overrides button styles or what not. With !important you can tell the browser to use that one even though it’s not the latest definition.
So it would be like
a.aio-orange, a.aio-orange:link, a.aio-orange:hover, a.aio-orange:visited, a.aio-orange:active, a.aio-orange:focus {
color: #FFF !important;
}
Or something like that.