Set a background color

To change the background color of all slides, write:

body {
    background-color: #191919; /*Insert your hex or rgb color code instead of #191919*/
}

CODE

To give the title slide a different color, write:

.reveal .title-slide .slide-background-content {
    background-color: #fcba03; /*Insert your hex or rgb color code instead of #fcba03*/
}

CODE