How do i change the hover button text color?

it will be much easier to help if we have a site to see your specific Button.

if you mean in general these shortcode buttons http://kriesi.at/themes/enfold/shortcodes/buttons/
there are rules for every defined color.

if you want to change every hover button text color you can add this:

.avia-button:hover {
    color: #0a2907 !important;
}

but if you want to change only one specific colored Button (and this makes sense because a gray in a silver button is not good) we had to see the example

in that case e.g.

.avia-button.avia-color-silver:hover {
    color: #0a2907 !important;
}