body {
    animation: colorchange 999s; 
    
    -webkit-animation: colorchange 20s;
}

@keyframes colorchange {
    0% {background: red;}

    25% {background: yellow;}

    50% {background: blue;}

    75% {background: green;}

    100% {background: red;}
}

@-webkit-keyframes colorchange
{
    0% {background: red;}

    25% {background: yellow;}

    50% {background: blue;}

    75% {background: green;}

    100% {background: red;}

    }