er-button>

A button should be styled with a background color, text color, ripple color
and hover color.

To style the background, text and hover color, apply the `background` and
`color` CSS properties to the button. To style the ripple color, apply the
`color` CSS property to the `#ripple` element in the button's shadow root:

    /* Style #my-button blue with white text and darker blue ink. */
    #my-button {
        background: #4285f4;
        color: #fff;
    }

    #my-button:hover {
        backgro