Abstract Button CSS, using Gblocks

Hello Team,

I am using Abstract theme, Gblocks. Below is the css I am using. I want button text color to be #000000 on focus/hover/active state. How to acheive that. And also would prefer a black border in #000000 upon hover.

.gb-button{
font-family: "Spectral", Sans-serif;
font-size: 0.9em;
font-weight: 500;
text-transform: uppercase;
text-shadow: 0px 0px 0px rgba(0,0,0,0.3);
letter-spacing: 3px;
word-spacing: 2px;
border-style: solid;
border-width: 1px 1px 1px 1px;
border-radius: 0px 0px 0px 0px;
box-shadow: 0px 0px 0px 0px rgba(0,0,0,0.5);}

.gb-button-wrapper a.gb-button {background-color: #000000; padding: 10px 20px;}

.gb-button-wrapper a.gb-button:hover, a.gb-button:active {background-color: #ffffff; text-color: #000000;}