/* The important part */
#countdown > *:not(.second)::after {
    content: " :";
    color: white;
}

#countdown {
    color: white;
    font-family: "Roboto", serif;
    font-size: 4rem;
    font-weight: 100;
    font-style: normal;
}

#countdown-phase {
    color: white;
}