Edit in JSFiddle

button {
    display: block;
}
button:active {
    background: green;
}
button:focus {
    background: green;
}

<button>Click me</button>
<button>No, me</button>
<button>Seriously, I click much better</button>
<button>Don't listen to that guy</button>
<button>I clicked before it was cool</button>
<button>Don't click me</button>