Hover button, background same color, text color changes on hover

I am trying to make a button with a green background. The text would change color on hover (background stays the same, only the text color changes). I tried the code below but it does not work :-(.

In the Tempera Theme Custom CSS:
.greenbutton {
font-family:”Trebuchet MS”, Helvetica, sans-serif;
background: #82B607;
font-size: 20px;
display: block;
width: 250px;
text-decoration: none;
padding: 10px;
}
.greenbutton a {
color: white;
}
.greenbutton:hover a {
color: #e619d5;
}

In the page html:
<div class="greenbutton"><center><a href="https://www.......com" target="_blank">my text</a></center></div>